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RA425 R72 Preventive medicine 




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Copyright, 1913, by 

Printed in the United States of America 



Digitized by the Internet Archive 

in 2010 with funding from 

Open Knowledge Commons 


This book has been written in response to a demand for a treatise 
based upon modern progress in hygiene and sanitation. The work is 
planned to include those fields of the medical and related sciences 
which form the foundation of public health work. So far as I know, 
no other book on the subject covers the broad field considered in this 
volume. The progress in hygiene and sanitation has been so rapid that 
the subject of preventive medicine has become a specialty, and its scope 
has become so broad that the question throughout the making of this 
book has been rather what to leave out than what to include. The facts 
here brought together are widely scattered in the literature and many of 
them are difficult of access; they have been collected for the convenience 
of the student of medicine and the physician, as well as those engaged 
in sanitary engineering or public health work. 

During twenty-three years of varied experience in public health 
work it has been my good fortune to have served as quarantine officer, 
in epidemic campaigns, in epidemiological investigations, and in public 
health laboratories, at home, on the Continent, and in the tropics. The 
fruits of these experiences are reflected in this book, which may be 
taken as representing my personal views gained in the field, in the 
laboratory, in the classroom, and in administrative offices. 

It is wellnigh impossible to prevent or suppress a communicable 
disease without a knowledge of its mode of transmission. This is 
the most important single fact for successful personal prophylaxis, as 
well as in the general warfare against infection; therefore, the com- 
municable diseases have been grouped in accordance with their modes of 
transference. Each one of the important communicable diseases is dis- 
cussed separately in order to bring out the salient points upon which 
prevention is based. The classification adopted is believed to be unique 
and should prove helpful to those who are especially concerned in the 

prevention of infection. 



The book may be considered in two parts, namely, that which deals 
with the person (liygiene) and tliat which deals with the environ- 
ment (sanitation). The first part includes the prevention of the 
coninumicablo diseases, venereal prophylaxis, heredity, ininninity, eu- 
genics, and similar subjects. The second part deals with our environ- 
ment in its relation to liealth and disease and includes a discussion of 
food, water, air, soil, disposal of wastes, vital statistics, diseases of occu- 
pation, industrial hygiene, school hygiene, disinfection, quarantine, isola- 
tion, and otlier topics of sanitary importance, as well as subjects of 
interest to health ofhcers. All the important methods used in public 
health laboratories are described. 

To have made this book in monographic style with references to 
authorities for every statement would have resulted in an unwieldy 
work of impractical size and form. The textbook style has therefore been 
adopted and citation of authorities for facts that are now well estab- 
lished has been regarded as unnecessary. In this respect it may seem 
that I have given scant credit to many workers from whose writings 
I have borrowed results, thoughts, and sometimes words or even sen- 
tences. At the end of each chapter will be found a list of references 
to articles or books that I have especially drawn upon, and I desire to 
acknowledge my obligations to these sources as well as to refer the reader 
to them for further study of particular subjects. I have also drawn 
freely upon my own previous writings and those of my co-workers in 
compiling tliis book. The chapter on "Disinfection" is based upon my 
book entitled : "Disinfection and Disinfectants," published by P. Blaki- 
ston's Sons & Co., Philadelphia, 1902. 

I have received generous help from a number of friends and it is a 
pleasure here to acknowledge especially my obligation to Dr. David L. 
Edsall for reading and correcting the chapter on "Diseases of Occupa- 
tion," to Dr. John F. Anderson and Dr. Joseph Goldberger for re- 
vising the chapters upon "Measles" and "Typhus Fever," to Prof. George 
C. Whipple for reading and improving the chapter upon "Water," to 
Charles T. Brues for many suggestions in the section upon insect-borne 
diseases, and to Prof. W. E. Castle for a similar service with the section 
on "Heredity." Dr. Charles Wardell Stiles has kindly furnished infor- 
mation concerning the relation of parasites to soil. I also desire to 
express my obligations to Prof. Arthur I. Kendall, Dr. Harold L. Amoss, 


Dr. LeT\as W. Hackett, Prof. William D. Frost, and Miss Emily G. 

It has been my object to give in this volume the scientific basis 
ujDon wliich the j)revention of disease and the maintenance of health 
must rest. Exact knowledge has taken the place of fads and fancies 
in hygiene and sanitation; the capable health officer now possesses facts 
concerning infections which permit their ■ prevention and even their 
suppression in some instances. Many of these problems are complicated 
with economic and social difficulties, which are given due consideration, 
for preventive medicine has become a basic factor in sociolog}^ 




I. — Diseases HA\^N■G Specific or Special Prophylactic Measures 1 

Smallpox and Vaccination : Historical Note, 1 ; Vaccination, 3 ; 
Vaccine Virus, 3; Methods of Vaccination, 8; Indices of a Suc- 
cessful Vaccination, 11; The Immimity, 14; Revaecination, 15; 
Claims for Vaccination, 17; Vaccination of Exposed Persons, 17; 
Dangers and Complications, 19; Government Control of Vaccine 
Virus, 21; The Unity of Cowpox and Smallpox, 21; Compulsory 
Vaccination, 22 ; Inoculation or Variola Inoculata, 23 ; Prevalence 
of SmaUpox, 25; Epidemiology, 27; Modes of Infection, 27; Re- 
sistance of the Virus, 28; Smallpox in the Vaccinated and Un- 
vaccinated, 29; Result of Vaccination in Germany, 33; Isolation 
and Disinfection, 33. 

Rabies: General Considerations, 36; Period of Incubation, 38; 
Entrance and Exit of the Virus, 38; Relative Danger of Bites, 
38; Viability, 39; Prophylaxis, 39; Local Treatment of the 
Wound, 40; Pasteur Prophylactic Treatment, 41. 
The Venereal Diseases : Syphilis, 50 ; Gonorrhea, 53. 
Venereal Prophylaxis and Hygiene of Sex: Attitude, 55; 
Education, 55; Registration of Cases, 57; Continence, 57; Per- 
sonal Hygiene, 58; Prostitution, 58; Medical Prophylaxis, 58; 
Segregation, 59. 

Preventable Blindness: Ophthalmia Neonatorum, 61; Preva- 
lence, 62; Prevention, 63. 

Tetanus: Etiology, 66; Incubation, 70; Resistance, 70; Prophy- 
laxis, 72. 

n. — Diseases Spread Largely Through the Al\^ne Discharges 74 

Typhoid Fe\t:r: General Considerations, 74; Prevalence, 75; 
Channels of Entrance and Exit, 80 ; Diagnosis, 80 ; Bacillus Car- 
riers, 83; Resistance of the Virus, 83; Typhoid Bacillus in Na- 
ture, 84; Modes of Spread, 86; Preventive Typhoid Inoculations, 
94; Management of a Case so as to Prevent Spread, 98; Sum- 
mary — Personal Prophylaxis, 100. 




Cholera: General Considerations, 101; Cause and Contributinc: 
Causes of Cholera, 102; Diagnosis, 103; Modes of Transmission, 
104; Imnumity and Prophylactic Inoculations, 108; Quarantine, 
109; Pei-sonal Prophylaxis, 110; Summary — Prevention, 110. 
Dysentery: Classification, 111; Modes of Transmission, 112; 
Resistance, 113; Immunity, 113; Pei-sonal Prophylaxis, 113. 
HooK^voRM Disease: Distribution, 114; Varieties of Hookworm, 
115; Modes of Transmission, 115; The Parasite, 116; Immunity, 
118; Resistance of the Parasite, 118; Prevention, 119; Collateral 
Benefits, 121. 

III. — Diseases Spread Largely Through Discharges from the 

Mouth and Nose 122 

Tuberculosis: General Considerations, 122; Difference between 
the Human and the Bovine Tubercle Bacilli, 123; Bovine Tuber- 
culosis in Man, 124; Modes of Infection, 129; Immunity, 135; 
Resistance of the Virus, 137; Prevention, 138. 
Diphtheria: General Considerations, 143; Modes of Transmis- 
sion, 144; Resistance, 149; Immunity, 149; Prevention, 149; Pre- 
vention of Post -diphtheritic Paralysis, 151; Prevention of Sen;m 
Sickness, 152; Historical Note, 153. 

Measles: General Considerations, 154; Immunity, 155; Resis- 
tance of the Virus, 156; Modes of Transmission, 156; Preven- 
tion, 158. 

Scarlet Fever: Modes of Transmission, 160; Immunity, 163; 
Prophylaxis, 163. 

Whooping Cough: Mode of Transmission, 166; Immimity, 166; 
Prevention, 167; Mortality, 167. 
Mumps, 168. 

Lobar Pneumonia : General Considerations, 168 ; Modes of 
Transmission, 169; Resistance of the A^irus, 169; Immunity, 170; 
Prevention, 170. 

Influenza: Immunity, 172; Modes of Transmission, 172; Pro- 
phylaxis, 173. 

Common Colds: General Considerations, 173; Prevention, 175. 
Cerebrospinal Fever: General Considerations, 176; Preven- 
tion, 179. 

IV. — Insect-borne Diseases 181 

General Considerations, 181. 

Insecticides: Preparation of the Room for Fumigation, 187; 
The Relative Efficiency of Insecticides, 188; Sulphur, 190; For- 
maldehyde, 191; Pyrethrum, 192; Phenol-eamphor, 193; Hydro- 



cyanic Acid Gas, 194; Bisulphid of Carbon, 195; Petroleum, 196; 
Arsenic, 197. 

Mosquitoes : Life History and Habits, 200 ; Destruction of Mos- 
quitoes, 202; Malaria, 207; Yellow Fever, 212; Dengue, 220; 
Filaiiasis, 222. 

FiiiES: General Considerations, 223; Life Histoiy of the Musca 
Domestica, 224; Life History of Stomoxys Calcitrans, 226; Flies 
as Mechanical Carriers of Infection, 226; Suppression, 230; 
Sleeping Sickness, 232; Pappataci Fever, 237. 
Fleas: General Considerations, 237; Pulicides, 240; Relation of 
Plague to Rats and Fleas, 240. 

Rats and Other Rodexts : General Considerations, 242 ; Breed- 
ing and Prevalence, 243; Migration, 244; On Vessels, 245; Food, 
245; Habits, 245; Plague in Rats, 246; Rat Leprosy, 248; Trichi- 
nosis, 248 ; Other Parasites, 248 ; Economic Importance, 248 ; 
Suppression, 249 ; Squirrels, 253 ; Plague, 254. 
Ticks: General Considerations, 261; Texas Fever, 263; Rocky 
Mountain Spotted Fever, 263; Relapsing Fever, 266; South 
African Tick Fever, 267. 

Lice: General Considerations, 268; Typhus Fever, 269. 

Bedbugs : General Considerations, 272 ; Suppression of Bedbugs, 
273; Kala-azar, 274. 

References, 274. 

V. — Miscellaneous Diseases 275 

Infantile Paralysis : General Considerations, 275 ; Resistance of 
the Virus, 277; Immunity, 277; Modes of Transmission, 277. 

Chickenpox, 280. . 

Glanders: Diagnosis, 281; Prevention, 284. 

Anthrax: Resistance, 285; Immunity, 285. 


Malta Fever: Modes of Transmission, 288; Goats' Milk and 
Malta Fever, 290; Resistance, 291; Prevention, 291. 
Leprosy : General Considerations, 292 ; Immunity, 293 ; Rat 
Leprosy, 293 ; Modes of Transmission, 294 ; Prevention, 296 ; 
Specific Prevention, 297. 

Mental Diseases (By Thomas W. Salmon, M. D.) : General 
Considerations, 298; Infectious Diseases Which Cause Insanity, 
299; Acute and Chronic Poisonings Which Cause Insanity, 301; 
Head Injuries and Insanity, 304; Heredity and Insanity, 304; 
Psychical Causes, 306 ; Economic Factors, 306 ; Immigration, ■ 
307; Agencies Available for the Application of Preventive 
Measures, 308. 



VI. — Some General Considerations 313 

Sources of Infection, 313; Modes of Transference, 314; Carriers, 
315; Missed Cases, 316; Channels of Infection, 316 ; "Contagious" 
and "Infectious," 317; Epidemic, Endemic, Pandemic, and Proso- 
demic, 317; The Management of an Epidemic Campaign, 319. 
Quarantine: General Considerations, 321; Maritime Quaran- 
tine, 322; Quarantine Procedures, 326; The Bill of Health, 327; 
Equipment of a Quarantine Station, 328; Qualifications of a 
Quarantine Officer, 328; Disinfection of Ships, 329; Cargo, 332; 
Ballast, 332; Foreign Inspection Service, 333; National versus 
State Quarantine, 333 ; Interstate Quarantine, 334. 


I. — Immunity 337 

General Considerations, 337; Mechanism of Immunity — Theories 
of Immunity, 338; Natural Immunity, 341; Acquired Immunity, 
343; Mixed Immunity, 343; How Immunity May Be Acquired, 
343; Specificity, 346; Local and General Immunity, 347; Bacillus 
Carriers or Immunitas Non Sterilans, 348 ; Latency, 350 ; Lowered 
Resistance, 351; Ehrlieh's Side-chain Theory of Immunity, 355; 
Antitoxic Immunity, 360. 

ToxiNES, 360. 

Antitoxins: General Considerations, 365; Gibson's Method of 
Concentrating Diphtheria Antitoxin, 370; Dried Antitoxin, 370; 
Mode of Action, 371. 
Endotoxins, 372. 

Tetanus Toxine: General Considerations, 373; Mode of Ac- 
tion, 376. 

Tetanus Antitoxin, 377. 

Standardization of Antitoxic Sera: Standardization of Diph- 
theria Antitoxin, 378; Standardization of Tetanus Antitoxin, 380, 

Phagocytosis, 384. 
Opsonins: The Opsonic Index, 388. 

Lysins: General Considerations, 388; Pfeiffer's Phenomenon, 389. 
Hemolysis, 392. 
Cytotoxins, 393. 

The Bordet-Gengou Phenomenon — Fixation of Comple- 
ment^ 394. 



The Neisser-Wechsbeeg Phenomenon or Deviation op the 
Complement^ 395. 

Isohemolysins, 396. 

Precipitins : General Considerations, 396 ; Tests for Blood, 399. 
Agglutinins, 400. 

Anaphylaxis : General Considerations, 403 ; Examples of Ana- 
phylaxis, 404; Experimental Sernm Anaphylaxis, 404; Specificity, 
406; Sensitization by Feeding, 408; Maternal Transmission, 408; 
Serum Anaphylaxis in Man, or Serima Sickness, 408; Hypersus- 
ceptibility and Immunity Produced by Bacterial Proteins, 411; 
Relation of Anaphylaxis to Protein Metabolism, 411; Relation of 
Anaphylaxis to Endotoxins, 412 ; Relation of Anaphylaxis to 
Tuberculosis, 412; Relation of Anaphylaxis to Vaccination, 413; 
Other Practical Relations of Anaphylaxis, 413. 
References^ 414. 

II. — Heredity and Eugenics 415 

General Considerations, 415 ; Prevention of Propagation of Defec- 
tives, 416 ; Statistics of Defectives, 418 ; Degenerate Families, 419. 
Eugenics, 423. 

Principles of Heredity : Variation, 425 ; Darwin's Theoi-y, 425 ; 
Mutation, 426; De Vries — Discontinuous Evolution, 427; Weis- 
mann's Views, 427; Mendel's Law, 428; Atavism and Reversion, 
432; Galton's Law of Filial Regression, 433. 
The Cell in Heredity^ 434. 
Biometry, 436. 

Heredity versus Environment, 440. 
Immunity Gained Through Inheritance, 440. 

III. — The Hereditary Transmission of Disease . . . . 442 

General Considerations, 442; The Mierobie Diseases, 445; Hered- 
itary Transmission of a Tendency to a Disease, 445; Tubercu- 
losis, 446; Syphilis, 446; Cancer, 448; Leprosy, 448; Deaf- 
mutism, 448; Albinism, 448; Color-blindness or Daltonism, 449; 
Hemophilia, 450; Gout, 451; Brachydactylism, 451; Polydac- 
tylism, 451; Myopia, 451; Cataract, 451; Retinitis Pig-mentosa, 
451; Diabetes Mellitus, 452; Orthostatic Albuminuria, 453; Al- 
eohoUsm, 453; Epilepsy, 453; Huntington's Chorea, 454; Fried- 
reich's Disease — Hereditary Ataxia, 455; Imbecility, Defectives 
and Delinquents, 455; Insanity, 455. 
References, 457. 




I. — General Considerations 

The Uses of Food, 400. 

Classification of Foods, 461. 

Amount op Food: Excessive Amounts, 462; Insufficient Food, 

463; Unbalanced Diets, 464. 

Adulteration of Food, 465. 

Decomposed Foods: General Considerations, 468; Fermentation 

and Putrefaction, 469; "Ptomaine" Poisoning, 469. 

Preservation op Foods : General Considerations, 473 ; Cold, 474 ; 

Drying, 477; Salting and Pickling, 479; Jellies and Preserves, 

480; Smoking, 481; Canning, 481; Chemical Preservatives, 483. 

Preparation op Food: Cooking, 491; Methods of Cooking, 492. 

II. — Animal Foods : Milk ........ 

General Considerations, 494; Composition, 495; Milk Standards, 
499 ; Ferments or "Life" in Milk, 500 ; "Leukocytes" in Milk, 502 ; 
Excretion of Drugs in Milk, 503 ; Differences between Cow's Milk 
and Woman's Milk, 503; Classification of Milk, 504; Decomi^osi- 
tion of Milk, 506; Bitter Milk, 508; Colored Milk, 508; Adul- 
terations of Milk, 509 ; Dirty Milk— The Dirt Test, 509 ; Bacteria 
in Milk, 509 ; Germicidal Property of Milk, 511 ; Diseases Spread 
by Milk, 512; Character of Milk-borne Epidemics, 516; Fresh 
Milk Products, 517; Inspection, 518; Pasteurization, 518; Effect 
of Heat Upon Milk, 522. 

Bacteriological Examination op Milk: Number of Bacteria, 
523 ; Kinds of Bacteria, 524. 

Microscopic Examination: The Stewart-Slack Method, 525; 
The Doane-Buckley Method, 526; The Prescott-Breed Method, 526. 
Chemical Analysis of Milk : Total Solids, 527 ; Determination 
of Total Solids, 527; Determinalion of Fats, 528; Determination 
of Milk Sugar, 531; Determination of Proteins, 532; Water, 532; 
Reaction, 533; Specific Gravity, 534; Heated Milk, 535; Tests 
for Enzymes and Their Significance, 535. 
References, 537. 

TIL — Animal Foods: Meat, Fish, Eggs, Etc. 

Meat: Structure and Composition of Meats, 538; Nutritive 
Value of Meat, 539; Sources of Meat, 540; Recognition of Spoiled 
Meat, 540; Prevention, 541; Meat Presen-atives, 541; Meat In- 
spection, 542; Meat Poisoning, 552. 



Fish: Physiological Fish Poisoning, 564; Bacterial Poisons, 564; 
Fish Tapeworm, 565. 

Shellfish: General Considerations, 565; Mussel Poisoning, 567; 
Miscellaneous, 567. 
Bob Veal, 567. 
Eggs, 568. 

IV. — Plant Foods . .571 

Poisoning feom Plant Foods: Ergotism, 571; Lathyrism, 572; 
Mushroom Poisoning, 572; Potato Poisoning, 573; Beri-beri, 574; 
Pellagra, 577. 



I. — Composition of the Air 582 

General Considerations, 582; Oxygen, 584; Nitrogen, 585; Argon, 
585; Ozone, 585; Hydrogen Peroxid, 586; Ammonia, 586; Min- 
eral Acids, 587; Carbon Dioxid, 587; CO2 as an Index of Vitia- 
tion, 588; Methods for Determining Carbon Dioxid, 590. 

II. — Pressure, Temperature, and Humidity 598 

Pressure: Normal Atmospheric Pressure, 598; Diminished At- 
mospheric Pressure, 598 ; Increased Atmospheric Pressure, 600 ; 
Barometers, 601. 

Movements op the Atmosphere, 602. 

Temperature of the Air: Generar Considerations, 603; Methods 
of Recording Temperature, 604. 

Humidity: Aqueous Vapor, 605; Methods of Detennining Hu- 
midity in the Air, 610; Relation of Humidity and Temperature 
to Health, 613; Effects of Warm, Moist Air, 616; Effects of Cold, 
Damp Air, 616 ; Effects of Warm, Dry Air, 617. 

III. — Miscellaneous 619 

Odors, 619; Light, 620; Electricity, 621; Radioactivity, 622; 
Smoke, 622; Fog, 625; Dust, 625; Dust and Disease, 627; Meth- 
ods for Examining Dust, 628. 

IV. — Bacteria and Poisonous Gases in the Air .... 630 

Bacteria in the Air: General Considerations, 630; Method for 
Determining Bacteria in the Air, 631; Air and Infection, 632. 
Poisonous Gases in the Air: Carbon Monoxid, 635; Illumi- 
nating Gas, 636; Other Gases in the Air, 638. 
Sewer Gas : General Considerations, 638 ; Bacteria in Sewer Air, 
639; Ventilation of Sewers, 640. 



V. — Fresh and Vitiated Air 6il 

Benefits of Fresh Air, 641. 

Effects of Vitiated Air: General Considerations, 641; The 

Effects of Increased Carbon Dioxid and Diminished Oxygen, 643; 

Poisons in the Expired Breath, 644; Physical Changes in the 

Air, 647. 

Summary, 649. 

VI. — Ventilation and Heating 651 

Ventilation : General Considerations, 651 ; Vitiation by Respira- 
tion, 653 ; The Amount of Air Required, 654 ; Standards of Purity 
— Efficiency of Ventilation, 656; The Size and Shai^e of the 
Room, 657; Inlets and Outlets, 659; External Ventilation, 661; 
Natural Ventilation, 661 ; Mechanical Ventilation, 665. 
Heating: General Considerations, 665; Open Fires, 666; Frank- 
lin Stoves, 667; Open Gas Heaters, 667; Hot-air Furnaces, 667; 
Hot-water and Steam Pipes, 668; Electric Heating, 668; Cooling 
of Rooms, 668. 



I. — General Considerations 670 

Classification of Soils, 671; Surface Configuration, 671; Compo- 
sition of the Soil, 672; Soil Air, 674; Soil Water, 675; The 
Nitrogen Cycle, 676 ; The Carbon Cycle, 680. 

II. — The Soil and Its Relation to Disease 681 

Bacteria in Soil, 681; Pollution of the Soil, 682; Dirt, 683; 
Cleanliness, 684; Influence of Soil Upon Health, 684; Diseases 
Associated with the Soil, 685. 

I. — General Considerations 691 

Composition, 692; Classification of Water, 692; Properties of 
Water, 693; Uses of Water in the Body, 693; Amount of Water 
Used and Wasted, 694; Double Water Supplies, 697. 
Sources of Water: Rain Water, 698; Surface Waters, 702; 
Ground Water, 708. 

Sources and Nature of Water Pollution and Infection: 
General Considerations, 717; Simple Tests to Determine Sources 
of Pollution, 718; Interstate Pollution of Streams, 719; Care 
of Catchment Areas, 720. 



II. — Sanitary Analysis of Water . . . . . . . 722 

Standard Methods^, 722. 

Odors and Tastes: General Considerations, 723; Method of 
Determining Odor, 726; Prevention and Removal of Tastes and 
Odors, 727. 

Color: General Considerations, 728; Method for Estimating 
Color, 729. 

Turbidity : General Considerations, 729 ; Methods for Estimating 
Turbidity, 731. 
Reaction, 731. 

Total Solids: General Considerations, 732; Methods for Esti- 
mating Total Solids, 733. 

Hardness : General Considerations, 733 ; Methods for Determin- 
ing Hardness, 735. 

Organic Matter: Free Ammonia, 736; Albuminoid Ammonia, 
739; Nitrites, 741; Nitrates, 742. 

Chlorin : General Considerations, 744 ; Determination of Chlo- 
rin, 745. 

Oxygen: Oxygen Consumed, 746; Dissolved Oxygen, 748. 
Iron: General Considerations, 749; Iron Pipes, 750. 
Lead: Tests, 751. 
Expression of Chemical Results, 751. 

III. — Microscopical Examination of Water 753 

Methods of Microscopical Examination, 753; Significance of the 
Examination, 754. 

Bacteriological Examination : General Considerations, 754 ; 
Number of Bacteria in Water, 755; Kinds of Bacteria in Water, 
758; Colon Bacillus, 759; Sewage Streptococci, 761; Typhoid 
Bacillus, 761; Cholera, 761. 

IV. — Interpretation of Sanitary Water Analysis .... 763 

General Considerations, 763; Allowable Limits, 764; Illustrative 
Analyses Interpreted, 765. 

V. — The Purification of Water 776 

Nature's Method op Purifying Water : General Considerations, 
776; Evaporation and Condensation, 777; Self-purification of 
Streams, 777 ; Storage in Lakes and Ponds, 779 ; Sunlight, 779. 


Distilled Water, 780. 
Boiled Water. 7S0. 

Filters: Slow Sand Filters, 781; Mechanical Filters, 788; 
Household Filteis, 792; Serubbiuii or Roughing Filters, 793; 
Screening, 793. 
Storage, 793. 
Sedimentation, 794. 

Chemical Methods of Purifying Water: Ozone, 794; Chlo- 
rinated Lime Bleaching Powder, 797; Perniangaiuite of Potash, 
798; Alum or Sulphate of Alununum, 799; Metallic Iron: The 
Anderson Process, 800; Co^^per Sulphate, 800. 
Ultra-violet Rays, 801. 

VI. — Water and Its Relation to Disease 

General Considerations, 803. 
The Mills- Reincke Phenomenon, 804. 

Non-specific Diseases Due to Water: General Considerations, 
806; Goiter, 807; Lead Poisoning, 810. 

Specific Diseases Due to Water: General Considerations, 813; 
Cholera, 815; Typhoid Fever, 822; Dysentery, 834; Diarrhea, 
835; Malaria, 83G; Yellow Fever, 837; Animal Parasites, 837. 
Ice: General Considerations, 837; Natural Ice, 838; Manufac- 
tured Ice, 839; Properties of Ice, 840; Ice and Disease, 840. 
References, 842. 



By George C. Whipple 

General Considerations: Importance of Speedy Removal of 
Fecal Matter, 843; Dry Earth System, 844; Water Carriage Sys- 
tem, 844; Separate and Combined Systems, 845; Quantity of 
Sewage, 846; Composition of Sewage, 846; Ventilation and 
Flushing of Sewers, 848. 

Stream Pollution: Sewage Disposal by Dilution, 848; Hygienic 
Aspects of Stream Pollution, 850; Protection Against Pollution, 
851 ; Water Filtration. 851 ; Treatment of Sewage, 851. 
Cooperative Sanitation, 863. 
The Rural Problem of Sewage Disposal, 864. 
References, 868. 




By George C. Whipple 

General Considerations, 870; Incineration Plants, 872; Reduction 
Plants, 872; Feeding Garbage to Hogs, 873; Collection of Gar- 
bage, 873; References, 873. 



By Cressy L. Wilbur, M. D. 

General Considerations, 874; Necessity of Vital Statistics in 
Public Health Work, 875 ; Neglected Condition of Vital Statistics 
in the United States, 876; Collection of Vital Statistics, 878; 
Population, 8S8; Vital Rates, 888; Specific and Corrected Death 
Rates, 901 ; Classification of Causes of Death, 905 ; References to 
Sources and General Precautions in Use of Statistical Data, 908. 


General Considerations, 911. 

Some Fundamental Considerations in Prevention : General 
Considerations, 915; Hours of Work, 916; Fatigue, 916; 
Children, 917: Women, 918; Factory Inspection, 919; Pre- 
ventable Accidents, 920; Sedentary Occupations, 921. 
Diseases of Occupation: Classification of the Occupational 
Diseases, 921; Lead, 922; Phosphorus, 930; Arsenic, 934; Mer- 
cury, 935 ; Carbon Monoxid, 936 ; Hydrogen Sulphid, 937 ; Dusty 
Trades, 938 ; The Textile Industries, 939 ; Wood Dust, 941 ; Min- 
ing, 941; Effects of Heat, 942; Parasites, 943; Caisson 
Disease, 944. 




General Considerations, 945; School Building, 947; The School- 
room, 948; School Furniture, 949; Posture, 952; Lighting, 953; 


Ventilation and Heatinsr, 954; Water-closets and Urinals, 955; 
Cloak-rooms, 955; Cleanliness, 956; Medical Inspection of 
Schools, 956; The Conimuuicable Diseases of Childhood, 959; 
The Eyes, 959 ; The Eai-s, 961 ; The Teeth, 961 ; Nose and Throat, 
961 ; Diseases of the Skin, 962 ; Nervous Diseases and Mental 
Defects, 963 ; Vaccination, 964 ; References, 964. 



I. — General Considerations 966 

Definitions, 966 ; Nature's Disinfecting Agencies, 967 ; Cleanliness, 
968; Symbiosis, 968; When and Where to Disinfect, 969; Qualifi- 
cations of the Disinfeetor, 969; Controls, 969; Disinfection Must 
Be in Excess of Requirements, 970; The Ideal Disinfectant, 970; 
Terminal Disinfection, 970 ; Standardization of Disinfectants, 971. 

II. — Physical Agents op Disinfection 979 

Sunlight, 979; Ultra-violet Rays, 979; Electricity, 980; Burning, 
980; Dry Heat, 980; Boiling, 981; Steam, 982. 

III. — Chemical Agents op Disinfection 992 

Gaseous Disinfectants: Preparation of the Room, 992; For- 
maldehyd Gas, 993; Sulphur Dioxid, 997; Hydrocyanic Acid 
Gas, 1004; Chlorin, 1004; Oxygen, 1005; Ozone, 1005. 
Liquid Disinfectants : General Considerations, 1006 ; Methods of 
Using Chemical Solutions, 1008 ; Bichlorid of Mercury, 1009 ; 
Carbolic Acid, 1011; The Cresols, 1013; Formalin, 1014; Potas- 
sium Permanganate, 1015; Lime, 1016; The Hypochlorites, 1019; 
Antiformin, 1020; Bromin and lodin, 1021; Ferrous Sulphate, 
1021 ; Sulphate of Copper, 1021 ; Clilorid of Zinc, 1021. 
Acros, 1021. 
Soaps, 1022. 

Convenient Formula for Disinfecting Solutions: Bichlorid 
of Mercury — Con-osive Sublimate, 1023; Formalin, 1023; Milk 
of Lime, 1024; Carbolic Acid, 1024; Chlorinated Lime, 1024. 

IV. — Methods of Disinfection . . . . ' . . . . 1025 

Air, 1025; Rooms, 1026; Stables, 1027; Railroad Cars, 1028; 
Feces, 1030; Bed and Body Linen, 1032; Books, 1033; Cadavers, 
1034; Thermometers, 1034; Wells and Cisterns, 1034. 



1. — Vaccinia. Course of the eruption from the fourth to the 

ninth day ........ 12 

2. — Vaccinia. Course of the eruption from the tenth day . 13 
3. — Course of vaccination and revaccination ... 16 
4. — Eatio of mortality of variola for 10,000 of the population, 

in Boston, from 1841 to 1911, inclusive ... 26 
5. — Smallpox mortality per 100,000 of population in Breslau 30 
6. — Smallpox mortality per 100,000 of population in Vienna 31 
7. — Smallpox mortality per 100,000 of population in Prussia 34 
8. — Smallpox mortality per 100,000 of population in Austria 35 
9. — Chart showing relation of enforcement of muzzling law 

to prevalence of rabies in Great Britain ... 40 
10. — Curve showing death rate from typhoid fever in Albany 

before and after filtration of water .... 79 

11. — Influence of public water supplies on the typhoid fever 

death rate ........ 85 

12. — Immediate and striking effect of purifying a badly infected 

water supply upon the typhoid situation ... 87 
13. — Abrupt reduction in death rates from typhoid fever inci- 
dent to water purification in four American cities . 89 
14. — Hookworms, natural size ...... 115 

15. — Hookworm embryo ....... 115 

16. — Chart computed from the United States census report to 
show how the opening of schools in autumn increases 

diphtheria 144 

17. — A South African blood-sucking fly (Pangonia), illustrat- 
ing long proboscis to pierce heavy fur of certain 
animals ......... 183 


18. — Example of sealing doors for purpose of fumigation 
19. — Anopheles punctipenis ...... 

20. — Stegomyia calopus (female) ..... 

21. — Head of stegomyia calopus (male) 

22. — Eggs of stegomyia calopus ..... 

28. — Larva of stegomyia calopus . . . . 

24. — Pupa of stegomyia calopus ..... 




25. — House fly, showing proboscis in the act of eating sugar . 224 

26. — Eggs of house fly, as laid in a mass .... 224 

27.— Eggs of house fly 225 

28. — Larva? of house fly 225 

29. — Puparium of house fly . . . . . . . 226 

30.— Stable fly 226 

31. — Head, showing proboscis, stomoxys calcitrans . 227 

32.— Wing of stable fly 227 

33.— The "little house fly" 228 

34. — ^Wing of house fly, showing how it carries dust particles 229 

35. — The Hodge fly trap on a garbage can . . . 231 

36.— Tsetse fly 233 

37. — Various gnats ........ 235 

38.— The Indian rat flea 238 

39. — The common rat flea of Europe and North America . 239 

40.— The human flea 239 

41. — A squin-el flea ........ 241 

42. — General scheme for testing plague rat infection, city of 

Manila 259 

43. — Isolated plague-infested center, Manila, P. I. . . . 260 

44._The Texas fever tick 263 

45. — Roclrv^ ^Mountain spotted fever tick .... 264 

46.— The bedbug 272 

47. — A device for preventing rats traveling along hawsers . 325 
48. — The cell with its various combining groups, or side chains, 

known as receptors ....... 357 

49. — The toxin molecule, showing the haptaphore (combining) 

group, and the toxaphore (poison) group . . . 357 
50. — The first stage of antitoxin formation : a toxin molecule an- 
chored to a receptor ....... 357 

51. — The second stage: continued stimulation causes a repro- 
duction of receptors ....... 358 

52. — Third stage : the receptors beginning to leave the cell . 358 
53. — Fourth stage: the receptors have left the cell and float 

free in the blood — antitoxin ..... 358 

54. — The neutralization of a toxin by antitoxin: the free re- 
ceptors in the blood have united with the toxin = anti- 
toxic immunity ....... 359 

55. — The second order of immunity, showing complement 

and immune body ....... 359 

56. — The third order of immunity, showing an immune body 

having two affinities ...... 359 

• 57. — History of the family Zero ...... 420 



58. — History (condensed and incomplete) of three markedh^ 

able families ........ 423 

59. — Wilson's theory of inheritance modified by Locke . . 428 
60.- — Diagram showing the course of color heredity in the 
Andalusian fowl, in which one color does not com- 
pletely dominate another ..... 430 

61. — Diagram showing the course of color heredity in the 
guinea-pig, in which one color completely dominates 

another ......... 431 

62. — Model to illustrate the law of probability or "chance" . 437 

63. — Normal heredity curve . . . . . . ' . 438 

64. — Family history showing deaf-mutism .... 448 

65. — Family history showing polydactylism .... 452 

66. — Family history sho^^^ng Huntington 's chorea . . . 454 

67. — Family history showing feeble-mindedness . . . 456 

68. — L'nsanitary surroundings of a cow-bam .... 506 

69. — Conditions under which it is difficult to cleanse and disin- 
fect milk bottles and milk pails ..... 510 

70. — A dark, poorly ventilated cow shed, difficult to keep clean 517 

71. — Automatic temperature recorder for pasteurizers . . 520 

72. — Straus home pasteurizer ...... 521 

73. — Trichinella spiralis ....... 560 

74. — Tenia solium, the pork or measly tapeworm . . 563 

75. — Beef tapeworm ........ 563 

76. — Dibothriocephalus latus, the fish tapeworm . . . 565 
77. — Portable Haldane apparatus for small percentages of car- 
bon dioxid ........ 591 

78. — Petterson-Palmquist apparatus . . . . . 594 

79. — Fitz air-tester . 596 

80.— Wolpert's air-tester . . . . . . .596 

81. — Dewing Co. apparatus ....... 596 

82. — ^Diagram showing absolute humidity in grains at dilferent 

temperatures . . . . . . . . 607 

83. — Sling psychrometer ....... 610 

84. — Relative humidity table ...... 611 

85. — Dew-point apparatus . . . . . . . 612 

86. — Table showing the density of smoke, in accordance with 
the Ringelmann chart, which may be emitted from the 
various classes of stacks in Boston, ]Mass., and the dura- 
tion of such emission ...... 624 

87. — Magnus aspirator ....... 632 

88. — Double aspirator ,,.....• 632 



89. — The position of inlets and outlets, and their relation to 

the air currents in a room ..... 660 

90. — "Window ventilator ....... 663 

91. — Diagrammatic sketch of various provisions for ventila- 
tion ......... 664 

92. — The nitrogen cycle ....... 677 

93. — The nitrogen cycle in diagrammatic vertical section . 678 

94.— Ground water 708 

95. — Usual method of pollution and even infection of wells 712 

96. — Proper construction of a well ..... 713 

97. — Popular idea of how wells become infected from surface 

pollution ........ 714 

98. — Depression of the ground water level by pumping and ten- 
dency to draw nearby pollution from the soil or cesspool 715 
99. — In a limestone formation it is difficult to tell anything 

about the source of water obtained from a well . 715 
100. — Spring exposed to contamination from surface washings 
from the hill above. Spring protected from surface 
washings, and with bucket which can be filled without 

contaminating the flow ...... 717 

101. — Algae: uroglena ; spirogyra; resting spores of spirogyra: 
chlamydomonas showing resting condition and repro- 
ductive bodies ........ 724 

102. — Algse: clathrocystis ; anabasna; oscillatoria ; asterionella ; 

navicula showing structure of diatom . . . 725 

103.— The oil droplets in a diatom 726 

104. — Diagram illustrating the character of the ground water in 
relation to soil pollution, to assist the interpretation of 

a sanitary analysis ....... 765 

105. — Diagram showing the location of samples . . . 775 

106.— Section of an English filter bed 782 

107. — The arrangement of a slow sand filter .... 783 

108.— Diagram illustrating "loss of head" . . . • . 786 

109. — Asiatic cholera and the Broad Street pump, London, 1854 816 

110. — Asiatic cholera and the Broad Street well, London, 1854 819 

111. — Map showing Hamburg water supply .... 821 

112. — Change in water supply ...... 824 

113. — Mean death rates from typhoid fever, 1902 to 1906, in 

66 American cities and 7 foreign cities . . . 825 

114.— Map of Plymouth, Penn., in 1885 828 

115. — Map showing water supply of Ashland, Wis. . . 830 

116. — Typical section of an Imhoff tank .... 853 



117. — Imhoff tanks and sludge drying beds, Emscher District, 

Germany ........ 851 

118. — Chemical precipitation plant at Worcester, Mass., inlet . 855 

119. — Chemical precipitation plant at "Worcester, Mass., outlet 855 

120. — Triple contact beds at Hampton, England . . . 856 
121. — Inclined screen, operated by water wheel, Birmingham, 

England 857 

122. — Trickling filters and final settling basin and roughing 

filter at Hj'de, England ...... 858 

123. — Trickling filter at Birmingham, England . . . 859 
124. — Removing sludge from a septic tank at Manchester, 

England ........ 861 

125. — Septic tank and chemical precipitation tanks at Rochdale, 

England 862 

126. — Bur^'ing sludge from hydrolytic tank at Hampton, Eng- 
land . . . 863 

127. — Chemical precipitation tanks at Glasgow, Scotland. Lower 

end 865 

128. — Chemical precipitation tanks at Glasgow, Scotland. Upper 

end ......... 865 

129. — Intermittent sand filtration bed at Brockton, Mass. . 866 
130. — Filter bed with sand ridged for winter operation at 

Brockton, Mass. ....... 867 

181. — Discharge of sewage upon a filter bed at Brockton, Mass. 868 
132. — Red oxid of lead and litharge, being mixed in the manu- 
facture of storage batteries ..... 913 

133. — An effective dust-removing system in the boot and shoe 

industry ......... 917 

134. — System of hoods and ventilators to carry off the fumes 

from the furnaces in a foundry ..... 921 

135. — A worker with lead oxid, showing respirator to protect 

himself against the poisonous dust .... 925 

136.— The stone industry 929 

137. — Workman exposed to zinc fumes in brass casting, causing 

a condition known as "brass-founders' ague" . 933 
138. — Drum with nails which combs out the small pieces of 

broom corn ........ 938 

139.— Faulty posture 950 

140. — The Heusinger desk ....... 951 

141. — Boston school-desk and chair . . • . . . . 952 

142. — Device for determining carbolic coefficients . . . 973 

143. — Hot air sterilizer 981 

144. — Section through Arnold steam sterilizer .... 983 



145. — Section through autoclave .... 

146. — Brarawell-Deane steam sterilizer . 

147. — Cross section through steam disinfecting chamber 

148. — Longitudinal section through steam disinfecting chamber 986 

149. — Kiuyoun-Francis steam disinfecting chamber . 

150. — Automatic thermometer ..... 

151. — Plan showing the method of installing the double-ended 

steam chambers at a national quarantine station . 
152. — Chart showing application of steam under pressure 
153. — Flaring top tin bucket for generating formaldehyd by the 

permanganate method . . . . . . 

154. — The pot method of burning sulphur 

155. — Large stack burner for sulphur, with 15 of the 18 pans 

removed to show construction .... 
156. — Liquefied sulphur dioxid in tin can 
157. — Section through sulphur furnace .... 













The prevention of smallpox depends primarily upon vaccination^ sec- 
ondarily ujDon isolation and disinfection. Yaccination was the first 
specific prophjdactic measure given to man; it produces an active im- 
munity to smallpox (variola). On account of its importance and great 
practical value this subject Tvill be considered in some detail^ for much 
of the antivaccination sentiment is due to ignorance or misconstruction 
of the facts. 

Historical Note.' — The credit of giving vaccination to the world is 
due to Jenner, who proved through carefully planned experiments that 
cowpox protects against smallpox. This fact had been familiar to the 
farmers and folk of England as a vague tradition for a long time. A 
young girl who sought medical advice of Jenner, when a student at 
Sudbury, said, "I cannot take smallpox because I have had cowpox" ; this 
remark made a strong impression upon the young medical student. 

Benjamin Jesty, a Dorchestershire farmer, in 1774 successfully vac- 
cinated his wife and two sons. Plett, in Holstein, in 1791 also success- 
fully vaccinated three children. It was Jenner, however, who through 
logical and scientific methods proved that a person who has had the 
mild disease, cowpox, enjoys jirotection against the serious and often 
fatal disease, smallpox. Waterhouse and others soon repeated and cor- 
roborated Jenner's experiments and helped to establish the soundness 
of his conclusions. 

Jenner made his crucial experiments in 1796, when he transferred 
the vaccine matter from the hand of a dairy maid (Sarah Xelms) to 
the arm of a boy about 8 3'ears old — name not given. Sarah Xelms 



scratched her hand with a thoru and "was infected with the cowpox 
from hor master's cows, in May, 179G." Jenncr transferred the vaccine 
virus from the eruption upon the hand of Sarah Nelms to the arm of 
the 8-year-old boy on May 14, 179G. A typical take followed. "In 
order to ascertain whether the boy, after feeling so slight an affection 
of the system from the cowpox virus, was secure from the contagion of 
the smallpox, he was inoculated the first of July following with variolous 
matter, immediately taken from a pustule. Several slight punctures 
and incisions were made on both arms, and the matter was carefully in- 
serted, but no disease followed. The same appearances were observable 
on the arm as we commonly see when a patient has had variolous mat- 
ter applied, after having either the cowpox or the smallpox. Several 
months afterward he was again inoculated with variolous matter, but no 
sensible effect was produced on the constitution." 

In addition to such direct experimental proof, Jenner inoculated 
smallpox matter into ten persons who had at some previous time con- 
tracted cowpox. 

Date of Inoculation 

Ascertained to 

with Smallpox 

1. 1778 

2. 1791 

3. 1792 

t \ 1 ' 95 

Mrs. H. 
Mary Barge 
Sarah Portlock 
{ Joseph Merret 
{ William Smith 

Have Had Cowpox 
When very young 
31 years previously 
27 years previously 
25 years previously 
1, 5, 15 years previously 

7. ( 1797 


9. After 1782 

r Elizabeth Wynne 
) Sarah Wynne 
( William Rodway 
Simon Nichols 

10 months previously 
9 months previously 
38 years previously 
Some years previously 

10. Not stated 

John Phillips 

53 years previously 

In justification of such human experimentation it should be re- 
membered that at that time the inoculation of smallpox matter into 
healthy individuals was an acknowledged method of preventing that 
disease. Jenner himself was inoculated when a boy. The question of 
"inoculation" (with smallpox) as contrasted with "vaccination" (with 
cowpox) will be discussed presently. 

With such proof as this Jenner put a popular belief upon a scien- 
tific basis. He demonstrated that cowpox is a local and trivial disease 
in man, that it may be readily transferred from man to man, and that 
it protects against smallpox. The chain of evidence was complete, but 
he first proved his thesis to his own satisfaction before he gave it to 
the world. He said himself: "I placed it on a rock where I knew it 
would be immovable before I invited the public to take a look at it." 
Jenner presented the results of his observations to the Royal Society, of 
which he was a Fellow, but the paper was refused. He then published 


it in 1798 as a book, modestly entitled, "An Inquiry Into the Causes 
and Effects of the Tariolse Yaccinge^ a Disease Discovered in Some of the 
Western Counties of England, Particularly Gloucestershire, and Known 
by the Xame of the Cowpox." Every student of preventive medicine 
should read this brief '"inquir}'" in the original. It may be taken as a 
model of accurate observation and logical presentation, showing great 
self-restraint and moderation of an observant, imaginative, and judicial 

Dr. Benjamin "Waterhouse, the first professor of Theory and Prac- 
tice of Physic in the Harvard Medical School, early became convinced 
of the value of Jenner's demonstration and obtained some vaccine virus 
from abroad. On July 8, 1800, he vaccinated his son, Daniel Oliver 
Waterhouse, then five years old. This was the first person vaccinated 
in America, so far as existing records show. Thomas Jefferson helped 
materially to spread the new doctrine in this country, and, in 1806, in 
writing to Jenner, said: "Future nations will know by history only 
that the loathsome smallpox has existed and by you has been extir- 
pated." This prophecy has not yet been fulfilled — though eminently 


Yaccination may be defined as the transference of the virus from 
the skin eruption of an animal having vaccinia or cowpox into the skin 
of another animal. For over one hundred years vaccination (from 
vaccn — a cow) was a specific term limited to the introduction of the 
virus of cowpox into the skin, in order to induce vaccinia and prevent 
variola. In recent years, however, the term has been used in a generic 
sense to include the introduction of many different substances in many 
different ways and for many different purposes. Thus we speak of 
attenuated or killed bacterial cultures as bacterial vaccines; and the 
subcutaneous inoculation of organic substances of diverse origin and 
nature is often spoken of as vaccination. TVe hear of typhoid vaccines, 
anthrax vaccines, staphylococcus vaccines, and we read in the litera- 
ture of animals "vaccinated"' with extracts of cancer and other organic 
substances. For distinction between a vaccine and a virus, see page 344. 


Yaccine virus is the specific principle in the matter obtained from 
the skin eruption of animals having a disease known as "vaccinia''' or 
"cowpox." Yaccine virus is obtained from calves, man, the buffalo, 
sometimes the camel, and other animals. 

Cowpox, or vaccinia, is an acute specific disease to which many 
animals are susceptible, namely, man, cattle, camels, rabbits, monkeys, 


guinea-pi gS;, rats, etc. The disease runs practically the same clinical 
course in all susceptible species. The eruption is always ^ local and 
confined to the site of the vaccinated area; the constitutional symptoms 
are always benijin and usually sli<f]it. Vaccinia or cowpox is a l)onign 
disease; when uncomplicated, it has never been known to cause death or 
leave any unpleasant sequela\ 

After an incubation ])eriod of from three to four days the local 
eruption begins as a ])apule which soon develops into a vesicle, and 
later into an umbilicated pustule. Surrounding the vesicle is a red- 
dened, inflamed, and tender areola. The neighboring lymph glands 
are swollen ami tender, and there is slight fever lasting several days. 
The pustule dries, leaving a crust or scab, which comes away, disclosing 
a typical foveated or pitted scar. 

Human and Bovine Vaccine Virus. — Vaccine virus may be obtained 
cithrr fi'om bovine or human sources. 

Human virus is now seldom used, for the reason that the supply 
would not be sufficient. Upon the appearance of a smallpox outbreak 
it is sometimes necessary to have enough virus to vaccinate from one 
hundred tliousand to a million people. Such large quantities evidently 
could not be obtained from man at any desired time. Another ol)jec- 
tion to the use of human virus is the possibility, although snuill, of 
transmitting syphilis, and perhaps other diseases. When Ininian seed 
is used the virus may be transferred directly from arm to arm ; or the 
virus may be preserved dry in the scab; or the contents of the vesicle 
may be kej)t in either a dried or moist state, as described below for 
bovine virus. Arm to arm vaccination is still practiced in several parts 
of the world, particularly in Mexico, where it is claimed that it has 
the advantage of prodi;cing a better take; that the results are surer in 
that there are fewer unsuccessful vaccinations; and, finally, it is stated 
that the human virus affords a better immunity, but as to this there 
is no proof and some doubt. 

Bovine virus has been used more or less since the time of Jenner, 
but especially since Copeman showed in 1891 how to purify it with 
glycerin. It has the great advantage of being readily obtained in any 
amount and when desired. It further totally eliminates the danger 
of conveying syphilis and other diseases peculiar to man. 

Forms of Vaccine Virus. — Vaccine virus may be used in one of 
three forms: (1) fresh, (2) dry, (3) glycerinated. 

The fresh virus may be taken from the eruption of the calf or man 
and transferred directly. Thus the Institut Vaccinale at Paris still 
prefers to use the fresh virus. The vesicle is squeezed at its base 1)e- 
tween the blades of forceps, and some of the contents are transferred 

^Eare exceptions to this statement will be noted later. 


directly from the calf to the skin of the arm by means of a thumb 
lancet or an}^ similar instrument. 

The vaccinal matter may be dried, and the virus remains potent in 
this state a very long time, especially if kept cold and protected from 
the light. The virus may be dried upon a splinter of ivory or other 
substance. Formerly physicians preserved the dried crust from a typi- 
cal take. Small portions of this crust were ground, moistened, and then 
inserted into the skin. 

Glycerinated virus consists of vaccine pulp treated with 60 per cent, 
pure glycerin. This purifies it and hence is preferable. Before taking 
up the question of gh'cerination, we must ' understand the difference be- 
tween vaccine lymph and vaccine pulp. 

Vaccine Pulp and Vaccine Lymph. — A distinction is drawn between 
the pulp and the lymph. The pulp consists of the entire vesicle. with 
its contents, which is scraped from the skin, and is composed of epi- 
thelium, leukocytes, bacteria, products of inflammatory reaction, the 
fluid content of the vesicle, debris, etc. The lymph is the serous fluid 
contained in the vesicle or which often exudes from the broken vesicle. 
When the eruption is produced on the skin of a calf in a large con- 
fluent area, the surface of the eruption is scraped away and the exuding 
lymph is placed upon points by dipping or brushing. Most of the active 
principle of vaccine virus is contained in the epithelial cells, and this 
portion i^ largely lost when only the lymph is used. The pulp, which 
includes the lymph, therefore contains the virus in greater concentration, 
and is almost exclusively used in this country at the present time. 

Dry Points Versus Glycerinated Vaccine Virus. — The old-fashioned 
dry points were prepared by dipping splinters of ivory into the vaccine 
lymph. Later the lymph was collected upon a brush and thus trans- 
ferred to the ivory point. Bone or glass may be sul^stituted for ivory. 
Bone is undesirable because it is exceedingly difficult to sterilize. The 
only advantage of the dry point is its convenience in vaccinating. Its 
disadvantage is that the virus dried upon such points cannot be purified 
as is the case with glycerinated pulp. Further, the points are used as 
scarifiers and the method of scarification favors irritation and infection 
of the wound. The dry points practically always contain more bacteria 
than the glycerinated virus. For these reasons dry points are no longer 
permitted in interstate traffic in accordance with the federal regulations. 

The superiority of the glycerinated virus will be evident from a 
study of the ripening or purification of vaccine virus with glycerin (see 
below) . 

The old-fashioned dry points must not be confused with the points 
now placed on the market by manufacturers containing a drop of glycer- 
inated lymph. There is no special objection to these, except that it 

encourages vaccination by the method of scarification. Some manufac- 


turers imitate the old-fashioned dn' point by reniovintr most of the 
glycerin from the rijiened pulp bv pressing it between l)lotting papers. 
The remaining pulp is then attached to the points with sterile dextrose, 
blood serum, or some other gummy substance. 

The Process of Ripening. — When the vaccine virus is fresh it is said 
to be "green." Glycerin is added to the green pulp, and after it has 
acted a certain period of time the virus is said to be "ripe." The use 
of glycerin for this purpose was introduced by Moncton Copeman in 
1891 for the purpose of preserving and purifying the virus. The glycer- 
in acts as a differential germicide, that is, it preserves ^ the active 
principle in the vaccine virus, but destroys the frail non-spore-bearing 
bacteria. In time the virus itself succumbs. Vaccine virus must, there- 
fore, not be used while green nor when too old. Manufacturers usually 
date their products as "not reliable after" or "return after" 4 to 6 
weeks in the summer time and 3 months during the cold season. 

Sixty per cent, glycerin of the best quality is used. I have shown 
that no growth of bacteria, yeasts, or molds takes place in this percen- 
tage. Two to four parts of 60 per cent, glycerin are added to 1 part of 
the pulp by weight. The mixture is then thoroughly ground with a 
mortar and pestle by hand, or between glass rollers in a special mill 
driven by machinery. The pulp should be thoroughly broken up and a 
uniform suspension obtained. The amount of glycerin added depends 
upon the consistency and character of the pulp. The only objection 
to adding more glycerin would be the greater dilution of the virus, and, 
therefore, a larger proportion of negatire takes. A higher percentage 
than GO per cent, of glycerin soon renders the virus inert. The glycerin 
probably destroys the bacteria Ijy virtue of its dehydrating action. The 
time required for the virus to ripen depends upon the temperature. 
Most of the non-spore-bearing bacteria perish in 30 days at 15° to 
20° C. Approximately the same effect may be obtained at 37° C. in 
from 24 to 48 hours. At low temperatures the glycerin has practically 
no bactericidal effect. The process must always be controlled bacterio- 

Substances other than glycerin are used for the purpose of purifying 
vaccine virus. Carbolic acid (0.5 to 1.0 per cent.) is used with success" 
in Japan, and to some extent in this country. Potassium c}anid, chloro- 
form, elilorobiitanol. etc.. liave been tried, with less success in practice. 

Bacteria in Vaccine Virus.- — Vaccine virus always contains bacteria. 
There is no such thing as asej^tic vaccine virus. The active principle 
has not been grown in pure cultures. However, the bacteria which con- 
taminate vaccine virus are, for the most part, harmless to man. They 
are commonly those that are found on and in the skin of the calf. The 

' Glycerin also serves as a preser\-ative for other filterable viruses, as foot 
and mouth disease, anterior poliomyelitis, rabies, etc. 


non-spore-bearing varieties are largely eliminated by the process of 
ripening. There are fewer bacteria in the typical unbroken vesicle than 
in a broken, crusty, inflamed eruption. Green virus may contain from 
a few thousand to over a million bacteria per cubic centimeter. The 
ripened, glycerinated virus contains comparatively much fewer, and these 
mostly spores of the hay bacillus, common molds, and other harmless 
saprophytes. The number of such bacteria in the ripened virus may 
be taken as an indication of the care and cleanliness with which the 
virus has been prepared. Staphylococci, streptococci, members of the 
hemorrhagic septicemic group, and, in a few instances, tetanus spores 
and the gas bacillus have been found in vaccine virus. 

Seed Vaccine. —The. seed virus may be obtained (1) from cowpox, 
(2) from smallpox, (3) by retrovaccination. 

Spontaneous or casual cowpox occasionally occurs, that is to say, the 
disease appears to arise spontaneously because its origin cannot be traced. 
Casual cowjDox comes either from another case of cowpox or from a 
case of smallpox. Cattle are not subject to smallpox, but, when small- 
pox virus is introduced into the skin of a calf, it produces cowpox. 
When smallpox is thus converted into cowpox, it remains fixed as such, 
and never reverts to smallpox.^ In several instances in England, Ger- 
many, and this country the seed virus has been obtained by starting 
cowpox through the inoculation of smallpox virus. Such virus should 
not be used until several transfers from calf to calf have been made, 
for the reason that some of the smallpox virus may be carried over 
unaltered, during the first few transfers. Eetrovaccination consists in 
carrying the vaccine virus back from child to calf. By this method its 
virulence is maintained. Instead of calves, monkeys or rabbits may be 
used for the purposes of retrovaccination. 

Propagation. — In the propagation of bovine virus young calves are 
preferred, because they are more manageable, the skin is more tender, 
and the eruption is therefore more abundant and typical. With young 
animals a milk diet may be used, which simplifies the problem of dust 
contamination from dry feed. If hay or fodder is used, it must first 
be autoclaved. Either heifers or bull calves are suitable. 

The animals are held in quarantine for seveiL days, under observa- 
tion, to determine the absence of infections such as tuberculosis, glan- 
ders, foot-and-mouth disease, tetanus, and skin eruptions of any kind. 

Before vaccinating the calf it is carefully cleaned, and the site 
of the inoculation is shaved and prepared surgically, but without the 
use of germicidal solutions. Germicides are not suitable for the reason 
that they are apt to destroy the vaccine virus. Cleanliness and asepsis 
are the watchwords. The area selected is usually the abdominal wall be- 

"^ It is highly significant that casual cowpox was formerly much more com- 
mon when smallpox was much more prevalent. 


tween the tip of the sternum and the groin, sometimes including the 
inner side of the thigli. The usual method is to make long, superficial 
incisions in the skin ahout one inch apart, and the seed virus is gently 
rul)bed into these incisions. The calves must then be kept rigidly iso- 
lated in a special room, moderately lighted, free from dust, and screened 
to keep out insects. The temperature of the animal is taken several 
times daily, and the eruption at each stage of the disease is closely 
watched and recorded. 

The virus is usually taken from the animal between the fifth and 
the eighth day. It is an advantage to take the virus as early as prac- 
ticable, in order to avoid contaminating infections which may occur 
when the vesicles supjmrate. Only typical and entirely characteristic 
vesicles should be removed. Before the virus is removed, the animal is 
killed to avoid pain, and an autojjsy is done as soon as the virus is re- 
moved. If the autopsy shows any lesions indicating infection? other 
than vaccinia, the virus is discarded. 

It is not wise in propagating vaccine virus to vaccinate too large 
an area. This favors infections by lowering resistance; less typical 
eruptions are obtained than when the area vaccinated is moderate in 
extent. A yield of from twenty to forty grams of pulp from one calf 
should satisfy the propagator. 

Before the virus is taken the animal is placed upon a special taljle, 
the site of the vaccination exposed and given a very thorough washing 
and prolonged scrubl)ing with soap, and an abundant flushing with 
sterile water. The pulp is usually obtained by scraping the vesicles 
with a sharp spoon curette. 

Glycerin (GO per cent.) in proper proportion is added at once to 
the pulp, and this is ground to a state of fine and uniform sulidivision 
in a Doring lymph mill, or simply by hand with a mortar and pestle. 
This glyccrinated pulp is then allowed to ripen, and when ripe it is 
hermetically sealed in capillary tubes, or placed in small vials, or upon 
glass or ivory points, for the market. 


Vaccination consists in transferring the virus from one animal to 
the skin of another animal. The operation may be compared to the 
transfer of a culture in a bacteriologic lal)oratory. Precisely similar 
precautions to prevent contamination must he used in both cases. Vac- 
cination must be regarded as a surgical operation. No person unfamiliar 
with surgical cleanliness should be permitted to perform this "little" 

The vaccine virus may be introduced in one of three ways: (1) by 
puncture, (2) by incision, or (3) by scarification. 


Jenner used punctures or short incisions. Later blisters were raised 
upon the skin and the virus placed upon the abraded surface. The 
incisions were then increased in number, and finally cross scratchings 
were made. 

Puncture.— The simplest and best method is puncture with a needle, 
for there is least chance of contamination and the eruption is typical. 
The disadvantage is that the virus now used is diluted with glycerin, 
and therefore somewhat attenuated, so that a few simple punctures are 
less apt to take. 

Incision. — The method advised and recommended is that of incision. 
Incision is the only method of vaccination permitted by the laws of 
Germany, and recommended by the Local Government Board of Eng- 
land. Incision, if not too deep, consists really of a series of punctures, 
and serves the same purpose. Incisions may be made with the point of 
a scalpel. I prefer to use a needle. The incision. or scratch should not 
be deep enough to draw blood, but a few drops do no harm. It is 
rather difficult to control the depth of the incision with a scalpel, espe- 
cially if it is sharp. Scratching with a needle is much more easily 
controlled. • The incisions should be about three-quarters of an inch 
long and about an inch apart. The vaccine virus is then placed upon 
the abraded surface, and gently rubbed, not ground, in. It is impor- 
tant not to cause any unnecessary irritation so as to avoid attracting 

Scarification. — Scarification or cross-scratching is prohibited in Ger- 
many by ministerial decree of March 31, 1897, which was incorporated 
into the revised rules of the Bundesrath, July 28, 1898. The objec- 
tion to scarification is that this method produces an abraded surface . 
which is soon covered by a crust of serum and blood, through which the 
eruption cannot pierce. The vesicles form a ring around the scarified 
area, leaving a central irritated wound, inviting infection. It is be- 
lieved that most of the cases of tetanus complicating vaccination oc- 
curred in cases in which scarification was used. In this method fa- 
vorable anaerobic conditions are produced under the crust or scab which 
forms over the abraded surface. 

The Point of Election.— The outer surface of the left arm at about 
the insertion of the deltoid is the most convenient for the operator and 
the patient. This is the original site selected by Jenner, and is less 
liable to severe glandular complications than other points. 

Flachs recommends the side of the chest at about the level of the 
sixth rib, in the axilla. Here the scar is not visible; there is little mo- 
tion, and it is easily bandaged, but this site is open to ihe disadvantage 
of greater heat and moisture and there is, therefore, greater danger of 

The leg is sometimes selected to avoid disfigurement, The vaccina- 


tion sear should not be regarded as a deformity. To tlie sanitarian a 
typical vaccine scar is a sanitary dinii)lc. 'J'he leg is more exposed 
than the arm to traumatism, and, therefore, to complications. Dock 
refuses to vaccinate on the leg unless the patient will stay in bed until 
the vesicle heals. With babies in diapers and with young children it is 
exceedingly difficult to keep these parts clean. If the leg is selected, the 
vaccination should be done on the calf below the head of the fibula, 
and not on the outer surface of the thigh. 

Number of Incisions.— This has an important bearing upon the 
probability of the take, as well as the ])rotection. It is not wise to de- 
pend upon one. The relation of the number of vesicles and the amount 
of reaction to the degree and length of the immunity has not been 
worked out. The German regulations of 1891) require at least four in- 
cisions, each one centimeter long, and two centimeters apart. The 
Local Government Board of England directs that four vesicles should 
be produced, and that the total area of the vesicle formation shall not 
be less than one-half a square inch. My own practice follows that of 
Dock, who makes not less than two incisions about an inch long and 
an inch apart; but in case of exposure to smallpox three or four such 
incisions are advisable. 

The Operation. — The skin at the site of the operation must be sur- 
gically clean, but need not necessarily be treated with antiseptics. If 
such are used, they must be carefully washed away in order not to 
destroy the activity of the virus. A thorough scrubbing with soap and 
water is necessary for a dirty skin. Washing with warm water followed 
by alcohol is usually enough. The alcohol should be permitted to evap- 
orate before the incision is made. In general, the less the skin is irri- 
tated the less is the danger of complications. Needles are particularly 
handy, as they may be flamed just before the operation, and are con- 
venient in saving time when many people are to be vaccinated. The 
vaccine virus is gently rubbed into the incision, not ground in, and then 
allowed to dry. No dressing is necessary at the beginning, but several 
layers of dry sterile gauze held in place by adhesive plaster do no 
harm, and serve as a protection. Pads, plasters, and shields of any sort 
are unwise, because by retaining heat and moisture they cause a soften- 
ing and breaking down ; in other words, they act like a poultice. Bath- 
ing need not be omitted, nor any of the ordinary occupations, but un- 
necessary use of the arm must be guarded against, as this increases the 
congestion, inflammation, and the chances of infection. 

Schamberg and Kolmer ^ have recently advised the use of a 4 per 

cent, alcoholic solution of picric acid on the vaccinated area 48 hours 

after the insertion of the lymph. This apparently does not interfere 

with the success of the vaccination. Schamberg and Kolmer believe 

1 Lancet, Nov. 8, 1911, CLXXXI, No. 4603. 


that the picric acid lessens the degree of the local inflammatory reaction 
and that the patients are not so apt to exhibit constitutional disturb- 
ances. It also decreases the liability of extraneous bacterial infection. 


The take must be typical and the clinical course characteristic, other- 
wise we have no assurance that the individual is protected against small- 
pox. The best indices of a successful take are : ( 1 ) the course of the 
eruption, (2) the general symptoms, and (3) the scar. 

The importance of knowing the skin lesions of vaccinia were in- 
sisted upon by Jenner. Every vesicle, scab, ulcer, or irritated wound is 
not vaccinia. No confidence should be placed in doubtful or atypical 
takes. The typical features of vaccination are singularly alike. The 
clinical course of a primary vaccination is as follows : 

Course of the Eruption. — The primary wound soon heals. Appar- 
ently nothing occurs for 3 to 4 days, which is the period of incubation. 
Then one or more small papules appear upon the skin where the vac- 
cine virus was introduced. The papule is small, round, flat, bright 
red, hard, but superficial. About the fifth day the summit of the 
papule becomes vesicular. The vesicle is at first clear and pearl-like. 
Umbilication soon develops as the vesicle enlarges. A deep, red, and 
swollen areola surrounds the vesicle and grows wider as the lesion ad- 
vances. This gives the picture of the "pearl upon the rose leaf" which 
constitutes the true Jennerian vesicle. By the seventh day the vesicle 
is full size, round or oval, flat on top, umbilicated, and contents clear. 
It is multilocular ; if pricked with a pin or accidentally opened only 
that portion of the lymph contained in the compartment opened will 
exude. By the eighth day it turns yellowish, the middle is fuller, fol- 
lowing which the so-called second umbilication develops. Meanwhile 
the areola deepens, widens, and may be swollen. The skin feels hot, 
is painful, and the axillary glands become enlarged and tender. About 
the ninth day the areola begins to fade and the swelling subsides. By 
the eleventh or twelfth day the vesicle rapidly dries, leaving a brown, 
wrinkled scab, which finally drops ofi^. It should never be removed, as 
it forms the best bandage. 

The scar is at first red, finally turns white, with the pits or fovea- 
tions so characteristic of true cowpox. 

General Symptoms. — The general symptoms vary. There are malaise, 
loss of appetite, sometimes nausea and vomiting, headache, pain in the 
muscles of the back, and other indications of a mild febrile reaction. 
The temperature may go to 38° or 38.5° C. between the third and 
seventh days. The febrile reaction bears no special relation to the size 
^nd number of the vesicles or to the areola, The nitrogen eliiriina,tion 

Eighth Day 

Ninth Day 

Fig. 1. — Vaccinia. Course of the Eruption from the Fourth to the Ninth Dat. 


Twelftli Day 

Fourteenth Day 

Tliirteeiitli Day 

Scar— Sixth Week 

Fig. 2. — Vaccinia. Course of the Eruption from the Tenth Day. 



increases about the tenth day for a sliort time. The blood changes re- 
semble those of smallpox, an early leukopenia and secondary leukocy- 

Secondary vaccinations often run an accelerated, milder, or modified 
course. with shortened jieriod.s of incubation (see re vaccination). 


The immunity appears about the eighth day of the vaccination. 
Layet puts the ])oint of safety at the ninth day, Burckhard at the elev- 
enth. These data are based ujion the early work with variolation, when 
persons were inoculated with smallpox at various ])eriods following vac- 
cination. Sacco got only local eruption by inoculating smallpox on the 
eighth to the eleventh days, and none after that. 

Vaccination protects not only against smallpox, but also against 
vaccinia. Curiously enough, the degree and length of immunity ap- 
pear to l)e greater against smallpox than against itself. It is irra- 
tional to attempt to fix a definite time for the duration of the immu- 
nity. This varies as in other infectious processes. It is known through 
experiment and experience that the immunity gradually wears off. Defi- 
nite protection on the average lasts about seven years. The degree of 
protection is usually al)Solute for some years, and then gradually fades. 
In this, as in other diseases, immunity is a relative term. Smallpox 
itself does not always protect against smallpox. Some people have two 
and even three attacks of smallpox. Such cases, however, are excep- 
tional, and it is also exceptional to have smallpox occur in an individual 
who has been ])roperly vaccinated. 

Careful statistics collected in Japan since 1879 show quite definitely 
the gradual diminution of the immunity, beginning with the second year 
after vaccination. Kitasato's table,' based on 951 cases, is as follows: 


1 year 13.6 per cent. 

2 years 32.9 

3 years 46.6 

4 years 57.3 

5 years 51.1 

6 years 63.8 

"Weil, in 1899, reported 72.5 per cent, of successful revaccinations 
after seven years, 80 jier cent, after eight years, 85 per cent, after nine 
3'ears, and 88.0 per cent, after ten years. 

It is a fallacy to state that, if a revaccination takes, the subject was 
therefore suscejitible. While this is usually true, it does not necessarily 

Wqurnal A. M. A., March 25, 1911, p. 889. 


follow. It is a still greater fallacy to state that, if a vaccination fails, 
the subject is therefore immune. This view may result in real harm. 
Vaccination may fail for many reasons — the operation may not have 
been properly done, or the virus may have been inert. Sometimes per- 
sons are unsuccessfully vaccinated three, four, or more times before a 
typical take is obtained. 

The nature of the changes in the body which produce the immunity 
are not understood. In this sense vaccination is still an empiric pro- 
cedure. We now know of many analogous instances, however, where 
an active acquired immunity is induced by means of an attenuated virus. 
The immunity produced by vaccine virus does not depend upon an anti- 
toxin. The blood, however, contains specific antibodies, shown by the 
fact that equal parts of blood serum from a calf two weeks after suc- 
cessful vaccination mixed with vaccine virus destroy its activity. 


The fact that the immunity wears off after a number of years makes 
it necessary to practice revaccination in order to afford a continuous 
protection. There is some difference of opinion as to just when it is 
best to vaccinate the second time. Ten years is too long a period, prob- 
ably, to depend upon in individual cases. One year — advised by some — 
is shorter than necessary in most cases. The five-year interval of Japan 
is good in many respects, but probably not better than revaccination in 
the twelfth year obligatory in Germany. 

The best time to vaccinate is in the first year before the second sum- 
mer, again at from ten to thirteen years. After this it is usually un- 
necessary to vaccinate again, unless there is particular danger of expo- 
sure to smallpox. 

All persons exposed directly or indirectly to smallpox should at once 
be vaccinated — imless they have had the disease or have recently been 
successfully vaccinated. There are no contraindications to vaccinating 
babies immediately after birth. 

The clinical picture of secondary vaccinations may be quite different 
from the typical take following a primary vaccination. These altered 
reactions were known in the time of Jenner, but were lost sight of until 
recently rediscovered, and their significance realized from studies in 

Eevaccinations may be divided into three groups: (1) they may run 
an unaltered course resembling prim.ary takes in all respects, showing 
that immunity to cowpox has disappeared; (2) they may run a slightly 
more rapid course in which the period of incubation is shortened and 
in which the height of the pustular stage occurs about the sixth day 
(this is known as the accelerated reaction) ; or (3) they may run a 

















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very much shortened, milder, and rapid course. The eruption may be 
only a small papule or an almost imperceptible erythema which soon 
disappears; the period of incubation is less than 24 hours. This is 
known as the immediate reaction and resembles a cutaneous tuberculin 
reaction in many respects. These altered reactions have been studied 
especially by Von Pirquet and are shown graphically in Fig. 3. 

The immediate reaction may be put to practical use in order to dis- 
tinguish smallpox from chickenpox. Thus, Tieche has shown that small- 
pox virus introduced into the skin of a person immunized by vaccination 
will show the typical immediate reaction; whereas the virus of chicken- 
pox is invariably negative. This test can be freed of all possible danger 
by heating the virus to 60° C. for 30 minutes, which does not seem to 
affect the reaction. 


1. If successful, it protects the individual against smallpox for a 
period which has not been determined mathematically for the individual, 
but which averages about seven years. 

2. The protection may be renewed by a second vaccination. 

3. Persons successfully vaccinated on two occasions are usually 
immune against smallpox for life. 

4. Vaccination and revaccination systematically and generally car- 
ried out confer complete protection to a community or a nation. In, 
other words, while the individual protection is not always perfect, the 
communal protection is absolute. 

5. A person vaccinated once and at a later time contracting small- 
pox as a rule has the disease in a less serious form than unvaccinated 
persons (varioloid).^ The degree of favorable modification of smallpox 
is in inverse jjroportion to the period of time elapsing between the vac- 
cination and the attack of smallpox. 

6. The beneficial effects of vaccination are most pronounced in those 
in whom the vaccine affection has run its most typical and perfect 


The question frequently arises whether persons exposed to smallpox 
should be vaccinated. The effect of vaccination during the period of 
incubation of smallpox is very interesting, and may be summed up as 
follows : 

The term varioloid was introduced by Thompson in 1820 to describe the 
mild and modified form of smallpox occurring after vaccination. The eruption 
in varioloid disappears more rapidly than in variola. Yolfert, Dornbleuth, and 
Harden showed that one vaccination was not sufficient protection against small- 
pox for a lifetime, that revaccination was necessary and that the clinical mani- 
festations of this vaccination are as different from those of the first vaccination 
as varioloid is from variola. 



1. Vaccination just l)e('()i'e or diirinij tlio priniai-y fever of small- 
pox does not inihu'nce the disease, nor does the vaeeinalion take. 

2. If the vaccination is done during the last stage of the period of 
incubation of smallpox, the two infections run their course side by side 
without influencing cacb other. 

3. If it is done about the sixth or eighth day of the period of in- 
cubation the vaccination takes and may modify the severity of the 

4. Vaccination done at the beginning of the incubation period in 
time to have the vaccine eruption reach maturity before the smallpox 
begins will prevent or abort tlie disease. This is shown in tlie follow- 
ing diagram : 


Toward the 

During the 

Early in the 

Middle of the 

end of the 


On the 




Fever, or 







2nd to 6th days 

Gth to 8th days 

9th to 14 th days 


. Variola 


Smallpox is 

Varioloid or 

Smallpox not 

Smallpox not 



mild case 





1 1 1 1 1 1 1 1 1 1 1 1 
J 3 4 5 6 7 8 9 10 11 12 13 14 

1 2 3 


Period of Incubation of Smallpox — in Days 

1 1 1 1 .1 1 1 1 1 1 1 1 

Primary Fever Eruption 

The vaccina- 

The vaccination 

The vaccina- 

The vaccination 

The vaccination 

tion takes. 


tion takes 2 or 
4 days before 
primary fever. 

takes and both af- 
fections run side 
by side. 

does not take (?) 

To produce the best results the vac- 

- Vaccinia 

cination should precede this period, 

so as to reach maturity before the 

onset of the primary fever. The 

vaccine vesicle reaches maturity 

about the 8th 


As we can never be quite sure just what stage in the period of in- 
cubation a given case may be in, it is always advisable to vaccinate 
exposed persons. Furthermore, little harm will be done if it is too 
late and the vaccine eruption is added to the smallpox. Indeed, Hanna, ^ 
presents claims to the effect that there is abundant evidence in mitigat- 
ing the severity of smallpox when vaccination is performed at any time 
after infection up to the day of onset and even afterward. 

^Public Bealih., July, 1910, XXIIT, No. 10, p. 351. 



The alleged danger from vaccination has been greatly magnified by 
the antivaccinationists. However, vaccination is not always a harmless 
procedure; it must be looked upon as the production of an acute infec- 
tious disease, and, although the disease is always mild and trivial, it 
must not be treated as trifling. The chief danger lies in the fact that 
we have produced an open wound, which is subject to the complications 
of any wound. Even a pin prick or a razor scratch may result in death. 
While the aggregate number of deaths resulting from the complications 
of vaccination may be considerable, the aggregate of the individual risk 
is so small as to be disregarded, especially when proper precautions are 
taken. Many of the infections after vaccination occur in those in whom 
the regard for cleanliness is slight, and who neglect the site of the wound. 
In recent years, owing to the improved quality of the vaccine virus and 
the introduction of aseptic methods, a bad sore arm is a rare occurrence, 
and serious complications still rarer. In any case, the danger connected 
with vaccination is infinitesimal when compared with the benefit con- 
ferred. The important complications are : 

Auto Vaccination. — This is usually due to scratching the virus into 
the finger, the nose, the mouth, the mucous membranes, or any part of 
the skin. When carried into the eye it may cause blindness. Physicians 
sometimes vaccinate their lips by blowing into vaccine tubes. In vac- 
cine establishments accidental vaccination of the hand is common. 

Generalized Vaccination. — This is sometimes reported, but is usu- 
ally a mistaken diagnosis. A generalized eruption of cowpox is ex- 
ceedingly rare, if it ever occurs. I have seen it in the calf after intra- 
venous injection of a large amount of the virus, in which case there is 
a prolonged period of incubation. 

Wound infections, such as ulcers, gangrene, erysipelas, abscesses, 
lymphangitis, suppuration of the axillary glands, and other septic infec- 
tions are now exceedingly rare, and should be treated with the usual 
measures to prevent their occurrence. 

Impetigo contagiosa occasionally occurs and may be a serious com- 
plication of vaccination, especially the bullous impetigo or pemphigoid 
forms, which presumably have their origin in cattle. 

Syphilis, tuberculosis, and leprosy are sometimes feared, but these 
are practically impossible with the use of bovine virus. In any case it 
is doubtful whether tuberculosis or leprosy could be so transferred. 

Tetanus deserves a special word. Several outbreaks have been re- 
ported in this country after the use of certain viruses. Willson in 1902 
found tetanus spores in the vaccine virus used in a New Jersey out- 
break. Glycerin does not destroy the tetanus spore. Many hundreds of 


examinations made in tlie Hygienic Laboratory at Washington have 
failed to discover a tetanus spore in a single vaccine point or tube. The 
occasional danger cannot be denied. It is probable, however, that the 
infection in some of these cases comes from outside sources. 

The occurrence of occasional stray spores in vaccine virus was demon- 
strated by Carini.^ Such vaccine, however, had proved entirely harm- 
less in thousands of cases. It is more than probable that the actual 
danger would begin if such occasional stray spores were allowed to ger- 
minate in the vaccine pulp through some serious fault in manipulation. 
It is conceivable that the vaccine pulp after removal from the calf or 
heifer, if not at once chilled, or if not at once mixed with glycerin, may 
form a very rich medium for anaerobic bacteria. Some carelessness or 
neglect just at this stage might prove disastrous if tetanus spores ac- 
cidentally present should multiply. The epidemic in this country in 
1902 reported by Willson ^ and MacFarland ^ may have been the result 
of some such occurrence. On the other hand, neglected vaccination 
wounds or those in Avhicli proper bandages or shields favor anaerobiosis 
may stimulate the germination of spores coming from without and lead 
to the occasional reported sporadic cases following vaccination. 

To prevent tetanus complications it is important to avoid scarification 
and irritation, also to avoid the use of shields and bandages which favor 
anaerobic conditions; to practice strict cleanliness, and to use vaccine 
virus that has been properly prepared and tested. Special tests for 
tetanus are now required by federal regulations of every lot of vaccine 
virus before it is placed upon the market. 

Foot and Mouth Disease. — The infection of foot and mouth disease 
has in one instance been demonstrated as a contamination of vaccine 
virus.* It is, however, impossible to convey foot and mouth disease to 
man through cutaneous inoculation. While no harm has been done to 
man, the contamination is undesirable, and special federal regulations 
now require vaccine virus to be tested from time to time to assure its 
freedom from this infection. 

As an illustration of how seldom complications are caused by vac- 
cination we have the results of Germany, where in thirteen years (1885- 
1893) 32,166,619 children were vaccinated. Of these 115 died within 
a few weeks or months after the operation, presumably of injuries in- 
cidental thereto. Of these at least 48 probably did not die as a direct 
result of the vaccination. 

The figures of recent years are still better, for it is now exceedingly 
rare for a death to be recorded as directly due to vaccination. For 

^CentraJbl. f. Bait., Orig. 1904, XXXVII, p. 1147. 
'Jour. A. M. A., 1902, XXXYIII, p. 1147. 
^ Jour. Med. Besearch, 1902, n. s. II, p. 474. 

* yUMer and Rosenau, U. S. Dept. of Agriculture, B. A. T. Circular 147, June 
16, 1909. 


example, in the PhilijDpine Islands in the past few years the United 
States authorities Yacciiiated 3,515,000 persons without a single death 
or any serious post-vaeeinal complications. 


By the law of July 1, 1902, the vaccine virus sold in interstate traf- 
fic in the United States must come from a licensed manufacturer. 
These licenses are issued by the Secretary of the Treasury only after a 
careful inspection of the plant, personnel, and product by a competent 
government officer. The licenses are good for one year only, and are 
reissued only after reinspection. The government regulations require 
each lot of vaccine virus to be examined carefully by modern bacterio- 
logical methods to determine the number of bacteria, and special tests 
must be made to determine the absence of pathogenic microorganisms. 
These tests include animal inoculations, as well as cultural methods. 
Special tests for each lot of vaccine must be made to determine the 
presence or absence of streptococci, tetanus spores, foot and mouth infec- 
tions, etc. The government does not guarantee the purity and potency of 
each package of vaccine virus, but through its inspections and frequent 
examinations of the virus on the market every confidence may now be had 
in the vaccine virus propagated by licensed manufacturers in this country. 


The unity or duality of these two diseases has been the subject of 
much contention. Jenner originally considered cowpox to he a modified 
smallpox. The successful experiments in Germam^, England, and this 
country, in which smallpox has actually been modified by passing 
variolous matter through calves has proved positively that we are dealing 
with two forms of one disease. Much of the vaccine virus used during 
the past hundred years was originally obtained from cases of casual 
cowpox. This virus has been shown by experience and experiments to 
protect against smallpox, which makes it highly probable that we are 
dealing with one disease. The parasite Cytorrliyctes variolce, discovered 
by Councilman, Brinckerholf, and Tyzzer, gives a probable explanation 
of how smallpox may, under certain circumstances, become attenuated. 
The life cycle of this parasite interpreted by Calkins indicates that the 
mild disease, cowpox or vaccinia, is due to the asexual phase in the life 
cycle of the parasite which lives and multiplies in the c}i;oplasm of the 
epithelial cell; smallpox is caused by the combined asexual and sexual 
cycle of the same parasite, the latter phase occurring in the nucleus of 
the epithelial cell. When the Cytorrliyctes varioIcB loses its power to gen- 
erate by sexual division it never again regains it; that is, while small- 


pox may be modified into cowpox, cowpox has never been returned to 

It seems plain that much of the so-called casual cowpox probably 
has its origin from smallpox through accidental inoculation in milking 
or handling these animals by persons having or recovering from variola. 
Once started, the propagation of the modified virus from cow to cow 
would be comparatively simple. 


Vaccination affords a high degree of immunity to the individual, and 
a well-nigh perfect protection to the community. To remain unvac- 
cinated is selfish in that such persons steal a certain measure of pro- 
tection from the community on account of the barrier of vaccinated 
persons around them. 

The laws ^ and regulations relating to vaccination in the several 
states of the United States show marked lack of uniformity. Compulsory 
general vaccination can be said to exist by law only in Kentucky, Rhode 
Island, and Porto Rico.- Arizona, Hawaii, Maryland, New Mexico, 
North Dakota have laws requiring vaccination of children. In recent 
years smallpox has been so mild in the United States that the case 
death rate has been as low as 0.2 per cent., or 1 death in 500 cases. 

Decisions in the various courts in the United States have held com- 
pulsory vaccination to be legal. A decision of the Supreme Court of 
the United States (Henning Jacobson vs. The Commonwealth of Massa- 
chusetts, April 1, 1905) upheld in every respect the statute, the validity 
of which was questioned vmder the Constitution. 

The liberty secured by the Constitution of the United States .... 
does not impart an absohite right in each person to be, at all times, and in 
all circumstances, wholly freed fi'om restraint. Real liberty for all could 
not exist under the opei'ation of a principle which recognizes the right of 
each individual person to use his own, whether in respect to his person or 
his property, regardless of the injuiy that may be done to others. 

Theoretically it would be ideal if all persons submitted to vaccina- 
tion and revaccination voluntarily. But experience has shown that this is 
impractical, and. wherever tried, has failed. The best results have always 
been obtained where vaccination has been compulsory, and, in my judg- 
ment, this is the only present means by which smallpox may bo eliminated. 

The world may learn a valuable lesson from the splendid results 
obtained in Germany through compulsory vaccination and revaccina- 

^ Kerr, J. W., "Vaccination, and Analysis of the Laws and Eegiilations Re 
lating Thereto in Force in the United States," Public Health Bull. 52. 

^ Massachusetts, in 1809, was the first state to enact legislation relative to 



tion. In England the ^'conscience clause'" allows man}- persons to re- 
main unvaccinated and thereby seriously diminishes the effects of the 
vaccination laws of that land. In Minnesota the state health authori- 
ties became weary of the clamor against compulsory vaccination and 
assisted in having "the law repealed. They said, in substance, to the 
people of the state: "Take your choice. Be vaccinated and protect 
yourself, or run the risk of contracting smallpox; if you get it, it 
is your own fault."" 




-Smallpox Deaths- 
1SS7 18S8 



Average per 
Million of 

S-vreden* 4,746,465 

Ireland* 4,S0S,72S 

Scotland* 4,013,029 

Germany* 47,923,735 

England* 28,247,151 

Switzerland 2,922,430 

Belgium 5,940,365 

Russia 92,822,470 

Austria 23,000,000 

Italy 29,717,982 

Spain 11,564,000 
































*Compulsor\' vaccination. 


The practice of inoculation must be carefully distinguished from 
that of vaccination. By inoculation we mean the introduction of small- 
pox matter into the skin of man. The disease thus produced is usually 
very mild, but is nevertheless true smallpox, and just as contagious as 

This phase of the subject may be made clearer by considering small- 
pox as existing in three forms: (1) variola vera or true smallpox; (2) 
variola inoculata or inoculated smallpox; (3) vaccinia, c•o^vpox. or 
modified smallpox. The differences between these affections are shown 
in the table on the following page. 

Emphasis must be placed on the fact that variola inoculata, while 
usually a mild disease, is just as communicable as true smallpox, and 
those who contract the disease in this way get true smallpox, often in 
serious or fatal form. Inoculation, therefore, protects the individual 
hut endangers the community. 



\'ariola Vera 

Variola Inoculata 

Vaccinia or Cowpox 

True smallpox. 

Inoculated amallpos. 

Modified and attenuated small- 

Only occurs in man. 

Occurs in man and monkeys. 

Man, monkeys, cattle, guinea- 
pigs, rabbits, rats, camels, and 
many other mammals. 

High mortality. 

Milder; rarely fatal; about 1 in 

Verj- mild ; never fatal. 

A general eruption, often 
confluent or hemorrhagic. 

A general eruption, fewer pus- 
tules (rarely over 200) ; seldom 
confluent or hemorrhagic. 

Always local and confined to the 
site of the vaccination. 

Highly contagious 

Equally highly contagious. 

Not contagious — contracted 
only by mechanical transfer 
of vaccine virus. 

Period of incubation 12-14 

S days. 

3-1 days. 

Inoculation is a ven' old custom. It was practiced by the Chinese 
from time immemorial. The method was introduced into western civili- 
zation through Lady !Mary Wortly Montagu, who learned of the method at 
Constantinople and had her own bo}' "engrafted" with successful result. 
In 1717 Lady ^lontagii wrote her now famous letter to her friend 
Sarah Chiswell. and the practice soon became popular in England 
(1721) and spread to America and the Continent. It was introduced 
into this country by Dr. Zabdiel Boylston at Boston. But the dangers 
were early realized and inoculation was soon replaced by vaccination. 
According to Plehn. inoculation is still practiced in central Africa. 

The method of inoculation is precisely similar to that of vaccina- 
tion. The matter is obtained from the vesicle or pustule of a case of 
smallpox. This material is then introduced into the skin by means of 
a pimcture, an incision, or tlirough an al)raded surface. The Chinese, 
it is said, practice inoculation by blowing the dried smallpox crusts 
into the nostrils. 

While inoculation has properly fallen into disuse, there are con- 
ceivable emergencies in which the practice would be justified. For 
example, on board ship or on an island or isolated place, in the absence 
of vaccine virus. Under such circumstances it would be essential to 
inoculate everybody at the same time. 

The inoculation of smallpox will always remain for the student of 
preventive medicine one of the most interesting episodes in the develop- 


ment of the sanitary sciences. It illustrates in the clearest manner 
some of the fundamental phenomena of infection, susceptibility, and 
immunity. It was animal experimentation on a huge scale, the like of 
which we shall never see repeated on man as the subject (Sedgwick). 
It is now a matter of regret that for the sake of science better advan- 
tage was not taken of the data. 


It is very difficult for us now to realize that smallpox was once much 
more common than measles and much more fatal. Many of those who 
recovered were disfigured for life, left blind, or with some other serious 
consequence of the disease. For centuries smallpox was one of the 
greatest scourges. It depopulated cities and exterminated nations. In 
Europe alone, where its ravages were comparatively slight, it killed 
hundreds of thousands yearly. In the 18th century, of which we have 
the best records, almost everybody had it before he grew up. Parents 
sometimes exposed their children to the disease in order to be through 
with it, just as they now sometimes do with the minor contagious 

Smallpox was formerly a disease of children. It was called "kinder- 
hldttern." Since vaccination protects the child, smallpox has now be- 
come more prevalent among adults. 

The distinguished mathematician, Bernouille,. estimated that 15,000,- 
000 people died of smallpox in 25 years in the 18th century. It has 
been estimated that 60 million people died of smallpox during that 
century. Haygarth gives an account of a smallpox epidemic in Chester, 
England, population 14,713. At the termination of the epidemic there 
were but 1,060 persons, or 7 per cent, of the population, who had never 
had smallpox. Many similar instances are cited in the literature. 
The French physician de la Condamine (1754) said that "every tenth 
death was due to smallpox and that one-fourth of mankind was either 
killed by it or crippled or disfigured for life." Sarcone (1782) esti- 
mated the number of persons in Italy who suffered from smallpox as 
90 per cent, of the population. 

Smallpox was introduced into the western hemisphere by the Span- 
iards about 15 years after the discovery of America. In Mexico within 
a short period three and one-half million persons are said to have died 
of the disease (Chapman). Catlin (1841) states that of 12,000,000 
American Indians 6,000,000 fell victims to smallpox. In Iceland, in 
1707, 18,000 perished out of a population of 50,000, that is, smallpox 
killed 36 per cent, of the total population in one year. 

A good example is that of Boston in 1752, population at that time 
15,684. Of this number 5,998 had previously had smallpox. During 
the epidemic 5^545 persons contracted the disease in the usual manner. 



and '^M"?-! tdok it by inoculation. 1,843 persons escaped from the town 
to avoid the infection. Tlicro were, therefore, left in the city but 174 
persons who had never had >niallpox. 








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Smallpox is still as serious as it was in former times. Thus, in 
five vears, from 1893-1897, 346,520 persons died of smallpox in sixteen 


countries. Of this number Eussia alone lost 275,502. Tliese figures are 
the more terrible when it is realized that these lives might have been 
saved by the use of a simple 2:)rophylactic measure within reach of all. 


Few of the acute infectious diseases show such a complete inde- 
pendence of conditions such as race, climate, soil, age, sex, and occu- 
pation, sanitary surroundings, etc., as does smallpox. • It thrives wher- 
ever the contagion is carried, and wherever it finds susceptible people. 
Probably no one is naturally immune. The susceptibility of the popu- 
lation varies, because a smallpox outbreak leaves so many immune. This 
is one reason why the disease recurs in waves. The mortality varies 
greatly in different epidemics. At times it is less than one per cent. ; 
it frequently reaches thirty per cent, and over. 

In 1901-1903 the mortality in the United States was as low as 2 per 
cent, and following that 0.5 per cent. These differences occurred in 
the prevaccination era as well as now. 

The epidemiolog}' of smallpox bears no relation to improved sanita- 
tion, which has diminished the prevalence of tuberculosis, typhoid, 
cholera, and has practically subdued typhus and relapsing fever. It is 
evident that general sanitation could not affect contagious diseases like 
smallpox and measles. Smallpox spares neither high nor low, the 
rich or poor; before the days of vaccination it counted many kings, 
queens, and princes among its victims. 


"We are still ignorant of the precise mode by which smallpox is 
conveyed. The view generally held is that the infection is air-borne 
and enters the system through the respiratory mucous membrane. It 
has been surmised that a local lesion may be produced in this favor- 
able soil, the so-called "'"propustule," from which general infection 
through the blood takes place. The blood infection is marked by a 
sharp onset (the initial symptoms), and the skin eruption is embolic in 
character. The objection to this view is that a careful search of 54 
cases in Boston by Coimcilman and his colleagues failed to find such 
a propustule. 

It is known that the Chinese inoculated the disease by placing a 
crust from the eruption in the nostrils, but whether the disease so 
produced was variola vera or variola inoculata is not known. 

The virus of smallpox is always contained in the skin lesions. Of 
this we have experimental evidence. It is also supposed to be in the 
expired air. This, however, has never been experimentally proven. 
The disease is contagious before the eruption appears. It is even be- 
lieved to be communicable during the period of incubation. Smallpox 


has always been taken as the type of the contagious diseases; the con- 
tagion is the most "volatile" of any of the diseases of man. This 
volatility, however, has been overestimated, and, while probably an air- 
borne infection, the radius of danger is contracted. English observers 
have long taken the view that smallpox may be blown for great distances, 
and they attribute the prevalence of smallpox to the windward of hos- 
pitals as an indication that the virus may be carried down the wind. 
My experience with the disease teaches me that the danger from such 
a source is practically nil. One may safely live next door to a smallpox 
hospital that is well screened and properly managed. The influence of 
flies and other insects, or surreptitious visiting, may account for the 
spread of this disease outside of hospital w^alls. 

In addition to more or less direct contact smallpox may be spread 
indirectly in a great variety of ways. The secretions from the mouth 
and nose doubtless contain the infection, and, while suspicion has not 
particularly fallen upon the feces and urine, it is probable that all the 
secretions and excretions from the body may be infective at some time 
throughout the disease, or during convalescence. Toys, pencils, books, 
letters, spoons, cups, towels, handkerchiefs, bedding, and objects of the 
greatest variety that have in any way come in contact with the patient 
may carry the infection. Under favorable circumstances the active 
principle may probably live for a considerable time upon fomites. 

Smallpox is not usually considered an insect-borne disease, but it is 
highly prol)al)le that a fly lighting upon a smallpox patient and get- 
ting its proboscis, feet, and other portions of its body smeared with the 
variolous matter, and then flying to a susceptible person, could thus 
readily transmit the infection. Other insects may by such mechanical 
transfer play a similar role. 


It is generally, and doubtless correctly, assumed that the active 
principle of variola has approximately the same resistance to external 
conditions as vaccine virus. This assumj^tion is confirmed by experi- 
mental evidence, which shows that the virus of smallpox is even more 
readily destroyed than the virus of cow-pox. Scientific data concerning 
the viability of variolous matter is meager, owing to the fact that this 
question can only be settled by prolonged and repeated experiments 
upon monkeys. Brinckerhoff and Tyzzer ^ found that variolous virus 
is less resistant to desiccation than vaccine virus; that variolous virus 
does not pass a Berkefeld filter and is attenuated by long exposure to 
60 per cent, glycerin. 

In general it may be said that variolous virus is killed by exposure 

to ordinary germicidal substances, both liquid and gaseous, in the 

^"Studies upon Experimental Variola and Vaccinia in Quadrumana, " 
Jour. Med. Eesearch, Vol. XIV, No. 2, Jan., 1906, pp. 223-359. 



strengths and time commonly employed. It succumbs in fact before 
the average non-spore-bearing bacteria. 

There is a probable exception to this statement in the case of car- 
bolic acid and the coal-tar disinfectants. McClintock and Ferry ^ have 
shown that such germicides as carbolic acid, cresols, and the like do not 
destroy the virulence of vaccine virus in 0.5 per cent, solutions in five 
hours' exposure. In this strength and time almost all non-spore-bearing 
bacteria would be destroyed. The inference is allowable that this class of 
disinfectants cannot be relied upon to prevent the spread of smallpox. 

The experience of over one hundred years offers convincing proof 
of the pronounced difference in the mortality and morbidity from small- 
pox in the vaccinated and the unvaccinated. The following table from 
Schamberg shows that, among thousands of cases of smallpox occurring 
in cities all over the world, the death rate from smallpox has been from 
five to sixteen times greater among the unvaccinated than among the 
vaccinated : 


Places and Time of Obsei^'ation 

France, 1816-1S41 

Quebec, 1819-1820 

Philadelphia, 1825 

Canton Vaud, 1825-1829 

Verona, 1828-1829 

Milan, 1830-1851 

Breslau, 1831-1833 

Wurttemberg, 1831-1835 

Camiola, 1834-1835 

Vienna Hospital, 1834 

Carinthia, 1834-1835 

Adriatic, 1835 

Lower Austria, 1835 

Bohemia, 1835-1855 

Galicia, 1836 

Dalmatia, 1836 

London Smallpox Hospital, 1836-1856 . 

Vienna Hospital, 1837-1856 

Kiel, 1852-1853 

Wurttemberg (no date) 

Malta (no date) 

Epidemiological Society Returns (no date) 

Total No. 
of Cases 

Death Rate per 100 










the Unvac- 























the Vac- 


























^Jour. of the Amer. Public Health Assn., June, 1911 (Vol. I, No. 6), p. 418. 

- Extract from papers prepared in 1857 by Sir John Simon, Medical Officer 
of the General Board of Health of England, and at that time laid before Parlia- 
ment with reference to the History and Practice of Vaccination. Published in 
first Eeport of the Eoyal Commission on Vaccination, 1889, Appendix 1, p. 74. 

^ Jour, of the Amer, Fiiblic Health Assn., June, 1911 (Vol. 1, No. 6), p. 418. 










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Before Vaccination 

1749- 4,453 

1750 C.ISO 

After Vaccination 



1757 10,241 

1758 7,104 

1759 3.910 

1760 3,568 

1701 5,731 

1762 9,389 

1763 11,662 

1764 4,562 

1765 4,697 

1766 4,092 

1767 4,189 

1768 10,650 

1709 10,215 

1770 5,215 

1771 4,362 

1772 5,435 

1773 12,130 




1779 15,102 

1780 3,374 

1781 1,485 

1782 2,482 

1783 3,915 

1784 12,456 

1785 5,077 

1786 071 

1787 1,771 

1788 5,402 

1789 0,704 

1790 5,893 

1791 3,101 

1792 1,939 

1793 2,103 

1794 3,964 

1795 6,740 

1796 4,503 

1797 1,733 

1798 1,357 

1799 3,750 

1800 12,032 

1801 6,057 

Total (53 years) 125,130 



1809 2,404 









Compulsory Vaccination 
in Infancy 



Total (20 years) 18,217 

1822 11 

1823 39 

1824 618 

1825 1,243 

1826 625 

1827 600 

1828 257 

1829 53 

1830 104 

1831 612 

1832 022 

1833 1,145 

1834 1,049 

1835 445 

1836 138 

1837 361 

1838 1,805 

1839 1,934 

1840 650 

1841 237 

1842 58 

1843 9 

1844 6 

1845 6 

1846 2 

1847 13 

1848 71 

1849 341 

1850 1,376 

1851 2,488 

1852 1,534 

1853 279 

1854 204 

1855 41 

'^The population in 1751 was 1,785,727: in 1855 it was 3,639,332. 
2 From 1749 to 1773, inclusive, deaths from measles are included. 
' First successful vaccination in Stockholm. 


In countries like Germany, Sweden, Ireland, Scotland, and England, 
where vaccination is more or less compulsory, there is comparatively little 
smallpox. In countries like Belgium, Eussia, Austria, and Spain, which 
have no compulsory vaccination laws, smallpox yearly claims many 
victims. See table 1, page 23. 


April 8tli, 1874, Germany passed a general compulsory vaccination 
and revaccination law. The law requires the vaccination of all infants 
before the expiration of the first year of life, and a second vaccination 
at the age of twelve. Since this law went into effect there have been 
no epidemics of smallpox in Germany, despite the fact that the disease 
has been frequently introduced from without. In 1897 there were but 
8 deaths from smallpox in the entire German empire — population 54,- 
000,000. Since then long periods have passed without a single death 
from smallpox. From 1901 to 1910 there were only 380 deaths from 
smallpox in Germany; during the same period there were 4,286 deaths 
from smallpox in England and Wales, with only about half the popula- 
tion of Germany; furthermore, many of the deaths in Germany were 
in foreigners : Thus in 1909, out of 26 deaths from smallpox, 13 were 
foreigners, 11 of whom were Eussians. In the huge German army there 
have been only two deaths from smallpox since 1874. One of these was 
a reservist who had not been successfully vaccinated. Germany has 
taught the world how to utilize Jenner's great demonstration. 


Isolation and disinfection are only secondary measures in prevent- 
ing smallpox. They cannot be regarded as substitutes for vaccination. 

Isolation should be carried out with strictness for the reason that 
smallpox is one of the most contagious of the communicable infections. 
While the patient should be isolated, it is not necessary to isolate the 
hospital by banishing it to an inconvenient or undesirable location. 
There is, in fact, no good reason why a smallpox hospital should not 
be one of the units of the general hospital for communicable diseases. 
In any event, there is no danger from a smallpox hospital situated upon 
a high road or near other habitations, provided always proper precau- 
tions are taken to prevent the spread of the disease. 

The smallpox hospital should not be a pest house, but should be 
as inviting and attractive as economic conditions justify. Smallpox 
should not be treated in the home. From" the standpoint of prophylaxis 
the hospital is the logical and best place to care for this and other com- 
municable infections. If smallpox is treated in the home, this should 

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only be permitted if skilled nursing and trained attendants can be pro- 

The room in which the smallpox patient is isolated should be simply 
furnished to facilitate cleanliness and to permit purification. It must 
be well screened and free from insects and vermin of all kinds. The 
room should be well ventilated. This may be accomplished by an open 
firci)lace, in which case the contagium, if contained in the outgoing air, 
is burned in exit. 

The nurse attending a case of smallpox should also be segregated, 
and all visiting should be strictly interdicted. A separate kitchen should 
be provided and care should be taken that the dishes be scalded and 
remnants of food burned. 

Bedding, underwear, towels, and other objects should not leave the 
sick room unless they are first boiled, steamed, or immersed in a suitable 
germicidal solution, such as bichlorid of mercury, 1-1,000, or formalin, 
10 per cent. Carbolic acid should not be trusted. 

For terminal disinfection either sulphur dioxid or formaldehyde 
may be used. Objects particularly contaminated or soon to be used 
by others should be given a separate and special disinfection. Finally, 
the room should be thoroughly cleansed, aired, and sunned. 

The patient must be regarded as the source and fountainhead of 
the infection, and measures should be used at the bedside to prevent 
the surroundings from becoming contaminated. Cloths, cotton, and 
other dressings that become soiled Avith the contents of the vesicles and 
pustules after they break should be burned. The urine and feces may 
be disinfected with chlorinated lime. The sputum and discharges from 
abscesses must be carefully disinfected by an approved method (see 
Section XII). As a rule, smallpox patients are not dismissed from 
quarantine until desquamation has ceased. This may be favored by 
the use of warm baths and a generous use of soap, also by anointing 
the skin with vaselin or a bland oil. Special attention should be given 
to the hair, which should be well shampooed, to the interdigital spaces, 
and the fingernails, as well as to all folds of the skin, before the patient 
is released. 

The management of smallpox epidemics is discussed on page 319. 


Synokyms. — Jlyclroph oh la ; Wasserscheu, Wu tJi , To Uicu th ( Ger- 
man) ; Lyssa (Greek) ; La liage (French). 

Eabies is an acute, specific, rapidly fatal infection commimicated 
from a rabid animal to a susceptible animal, usually through a wound 

^Collateral reading: "Facts and Problems of Eabies, " Stimson, Hyg. Lab. 
Bull. No. 65, U. S. P. H. & M. H. S. 


produced by biting. Man always contracts the disease from some lower 
animal, usually the dog. The infective agent must be inoculated into 
the tissues; the virus is harmless when ingested. Eabies may be re- 
garded as a wound infection. The specific principle is contained in 
the saliva of animals suffering with the disease. The infection, there- 
fore, may be conveyed by licking provided there are fissures or open 
wounds in the skin. It is also possible to introduce the virus through 
autopsy accidents and other unusual ways, but commonly it is intro- 
duced through wounds produced by the teeth of a rabid animal. 

Every mammalian animal is susceptible. Even birds may contract 
the disease. It is most common in dogs, but it also occurs frequently 
in wolves, Jackals, foxes, and hyenas. Eabies in cats is comparatively 
rare. Cattle, sheep, and goats are infected relatively in about the same 
degree. It is less common in horses. Swine contract the disease less 
frequently than other domestic animals. Skunks have the disease and 
sometimes transmit it to man. 

Although all mammals are susceptible to rabies, it is perpetuated in 
nature almost exclusively by the domestic dog, only to a small extent 
by wild animals of the dog family, and occasionally by skunks, cats, etc. 
Outbreaks have been reported under unusual circumstances. Thus 
Carini ^ reports an epizootic causing the death of about 4,000 cattle and 
1,000 horses in Sao Paulo, Brazil. There was no unusual prevalence 
of rabies in dogs at the time but it was noticed that bats, in broad 
daylight, attacked and bit the cattle, and Carini suggests that bats 
may have been the source of the extensive epizootic. The animals 
affected all died after a few days and the meat and hides were utilized 
but no mishaps have been known to follow. 

Eabies exists practically all over the world, except in Australia, and 
recently in England. It is most common in France, Beligum, and Eussia. 
In the United States 111 human deaths were reported in 1908. In 
the same year there were 535 localities in which rabid animals were 
reported; in 1911 there were 1,381 localities, and 98 deaths in man. 
In 1890 the United States census reported 143 deaths in 30 states, and 
in 1900 but 23 deaths. 

Eabies is remarkable in that the mortality is 100 per cent. After 
symptoms begin recovery never occurs in man or other animals. Jo- 
seph Koch (1910), however, describes an abortive rabies. The disease 
is peculiar in several other particulars, especially the period of incuba- 
tion, which is more variable and more prolonged than that of any other 
acute infection. 

Eabies is commonly supposed to prevail only during the hot months, 

but it may be just as bad in cold weather. In fact, exposure to cold 

seems to increase its virulence. More cases occur from April to Sep- 

^ Ann. de I' Inst. Pasteur, Paris, Nov., XXV, 11, p. 785. 


tember than from October to March in tliis climate, because dogs run 
abroad more freely at this season of the year. It is this fact, and not 
the temperature, that influences the prevalence of tlie disease. 

Period of Incubation. — From the standpoint of prevention it is for- 
tunate that the period of incubation of this disease is prolonged. This 
period varies from 14 days to a year or more. The average period is 
as follows: Man, 40 days; dogs, 21-40 days; hors^es, 28-56 days; cows, 
28-56 days; pigs, 14-21 days; goats and sheep, 21-28 days; birds, 14-40 

The period of incubation depends largely upon the site of the wound, 
the relation to the nerve, the amount and virulence of the virus. It 
requires about 15 days to induce an active immunity to the disease by 
means of the Pasteur preventive treatment. There is, therefore, usu- 
ally plenty of time, if the case is seen early, to prevent the development 
of symptoms. 

It is probable that tlie prolonged period of incubation is due in part 
to the fact that the living principle reaches the central nervous system, 
but remains dormant until favorable conditions permit multiplication 
and the production of toxic effects (Joseph Kocli). 

Entrance and Exit of the Virus. — The active principle of rabies 
occurs principally in the saliva and in the central nervous system. It 
may be in the saliva at least three days (possibly eight) before the ani- 
mal shows symptoms (Roux and Nocard). It is, therefore, sufficient to 
watch a dog that has bitten a person or another animal for ten days. 
If no symptoms of rabies appear during this time there is no danger 
of conveying the disease, and the Pasteur treatment is unnecessary. 

The virus may also be found in the adrenals, the tear glands, the 
vitreous humor, the spermatic fluid, the urine, the lymph, the milk, as 
well as all parts of the central nervous system and the peripheral nerves. 
It is also found in the spinal and ventricular fluids. It has not been 
demonstrated in the liver, spleen, blood, or muscles. 

The virus enters the system through the broken skin and follows 
the nerve trunks from the seat of injury to the spinal cord, thence to 
the medulla and brain. The route corresponds to that of tetanus toxin. 
The mode of invasion of the virus may explain why pain, throbbing, 
tingling, numbness and other nervous disturbances are the first symp- 
toms to occur in parts of the body that have received the virus. It 
also partly explains the variable period of incubation, which is shorter in 
wounds of the face than in wounds of the extremities. It also explains 
why the disease is more serious when the wounds are in parts of the 
body where there is an abundant nerve supplv. 

The Relative Danger of Bites. — Wolf bites are most dangerous on 
account of the savage character of the wound, and the virulence of the 
virus. Cat bites come next, and then dog bites. The relative danger 


of bites of other animals is as follows : foxes, jackals, horses, asses, cattle, 
sheep, pigs. There is no authentic instance of the transmission of the 
disease by the bite of man, though this may be possible. The bites of 
horses and other herbivora are less dangerous because their blunt teeth 
usually cause contused wounds without breaking the skin. 

Bites on exposed surfaces are more dangerous than through the 
clothing, because the saliva is wiped from the teeth and little or none 
enters the wound. Long-haired dogs and sheep often escape infection 
for the same reason. Bites upon the face are most apt to be followed 
by rabies. 

ISTot every person bitten by a mad animal develops rabies. Leblanc's 
figures are 16.6 per cent. The statistics are difficult to analyze, and it 
is almost impossible now to collect sufficient data. According to the 
most reliable data, it would seem that rabies develops in not less than 
one person in ten bitten by mad dogs, and not receiving the Pasteur 
treatment. Paltauf places the figures at 6 to 9 per cent. 

Viability.- — The virus of rabies in the spinal cord of rabbits dies in 
about 14 days when dried at 20° -22° C, if protected from putrefaction 
and light. Spread in thin layers, it dies in 4 or 5 daj^s, and exposed 
to the sunlight in 40 hours. It is quite resistant to putrefaction. In 
a decomposed carcass it may be recovered by placing some of the cen- 
tral nervous system in glycerin. The glycerin destroys most of the con- 
taminating bacteria, but j^reserves the virus. Eabies virus is completely 
destroyed at 50° C. in one hour, and at 60° C. in 30 minutes. It is 
not injured by extreme cold. Five per cent, carbolic acid for one hour, 
1-1,000 bichlorid of mercury for one hour, or a saturated solution of 
iodin in water completely destroys its virulence. 


The prevention of rabies is considered under three heads: (1) 
Treatment of the wounds; (2) the Pasteur prophylactic treatment, and 
(3) the control of the disease in dogs by muzzling and quarantine. 

The cauterization of the wound and the Pasteur prophylactic treat- 
ment are efficient preventive measures for the individual, but they are 
not the true and best methods of controlling and preventing rabies. 
The disease may be avoided, even exterminated, by an intelligent system 
of muzzling and quarantining of dogs. A high tax on dogs and leash- 
ing are only restrictive measures. In England, wdien the dogs were 
muzzled, rabies diminished. The law was repealed, owing to misplaced 
sympathy for the dog, and rabies promptly increased. The law was 
again enforced, and in about two years the disease disappeared (see the 
accompanying chart). Now a strict quarantine of six months is main- 
tained against dogs entering England. It is no longer necessary to 



muzzle dogs in England, but muzzles will again be required should the 
disease reappear. Consistent muzzling of all dogs for two years will 
practically exterminate rabies. In Australia there are few carnivorous 
animals, mostly marsupials; there rabies does not exist, for it has 
been kept out owing to early and effective quarantine measures. 

Fig. 9. — Chart Showing Relation of 
LENCE OF Rabies in Great Britain. 
number of persons who died of rabies 
sent cases in dogs. (Frothingham.) 

Enforcement of Muzzling Law to Preva- 
The figures in the cross-hatching indicate the 
in England and Wales. The ordinates repre- 

Prophylactic measures necessar}' to control the dog question are: 
the destruction of ownerless dogs; license fee and tag for all dogs; 
owners to be legally responsible for damage inflicted by their dogs; 
education of the dog-owning public concerning the spread of commun- 
icable diseases, especially rabies; compulsory reporting of all cases or 
suspected cases of rabies. Further special and temporary measures 
advocated are: muzzling; restraint with chains, leash, etc.; observation 
in quarantine, or killing of all animals bitten by dogs; disinfection, etc. 


Wounds produced by the bite of an animal in which there is any 
suspicion of rabies should at once be cauterized with fuming nitric 
acid. The acid is best applied with a glass rod very thoroughly to all 
the parts of the wound, care being taken that pockets and recesses do 
not escape. Thorough cauterization at once reduces the danger of wound 


complications, and experience demonstrates that wounds so treated at 
once, are practically never followed by rabies. Marie obtained conflicting 
results with local treatment in experimental rabies; Cabot obtained the 
best results in a series of extensive experiments with nitric acid. Poor ^ 
was able to save the lives of 45 per cent, of guinea-pigs by cauterization 
with nitric acid at the end of 24 hours. In the absence of nitric acid 
the actual cautery may be used. Strong antiseptics, such as carbolic 
acid and formalin, are less reliable. Nitrate of silver is valueless. In 
any wound produced by the bite of an animal the rule is to cauterize 
unless sure that the animal is not mad. 

It has been shown that the virus may remain alive and virulent in 
the scar for a long time, and it has become a question whether patients 
seen after the wound has healed should not have the scar excised; this, 
however, is not the present practice. 


This method of prophylaxis was announced December 6, 1883, by 
Pasteur, at the International Congress at Copenhagen, and on February 
24, 1884, he laid before the French Academy the details of his experi- 
ments and results. The next year Pasteur, with the help of Eoux and 
Chamberland, worked out the details of the method now used. 

The principle of the treatment consists in producing an active im- 
munity by means of an attenuated virus. The virus is attenuated by 
drying. The fixed virus contained in the spinal cord of rabbits dead of 
hydrophobia is the material used, for subcutaneous injection. 

Street Virus and Fixed Virus. — The distinction between fixed and 
street virus is of fundamental importance in reference to the question 
of immunity. Street virus refers to the virus obtained from mad 
dogs naturally infected. When this virus is inoculated into a rabbit, it 
reproduces the disease after a period of incubation of from 14 to 21 
days or more. This street virus may then be conveyed from rabbit to 
rabbit through a number of transfers. In the passage from rabbit to 
rabbit the virus becomes more virulent for rabbits, but less so for dogs 
and other animals. The period of incubation is progressively shortened, 
until finally the rabbits invariably sicken on the sixth or seventh day and 
die on the ninth or tenth. When the virus has reached this degree of 
virulence for rabbits, it is said to be "fixed," for the reason that its 
potency remains constant. In its passage through rabbits the modifica- 
tion from street virus to fixed virus is gradual. It is important to note 
that fixed virus, which has attained a high degree of virulence for rab- 

^ Collected Studies, Research Lab., Dept. of Health, City of N. Y., VI, 
1911, p. 25. 


bits, has lost imicli of its virulence for dogs, and is probably entirely 
avirulent for man. 

Proesclier ^ injected into himself the entire brain and medulla of 
a rahl)it (fixed virus), and anotlier entire brain into a volunteer. No 
ill eil'ects of any kind were noted in either case. A control rabbit in- 
jected willi a <>.(f-^ dilution of the same emulsion died in seven days 
with experimental rabies. 

Marx tested the fresh fixed virus upon monkeys in large doses, with 
negative results. Ferran in Barcelona in 1887 inoculated 85 persons 
with the fresh fixed virus as a pro])hylactic treatment for dog bites 
with good results, which have been further confirmed by Wysokowiez 
and Nitsch. The evidence points clearly to the fact that the fixed virus 
of rabbits does not pi'oduce rabies in man when introduced into the sub- 
cutaneous tissue. 

Preparation of the Virus. — Rabbits are injected under the dura 
mater with a few drops of an emulsion of fresh fixed virus obtained 
from the pons or medulla of another rabbit dead of hydrophobia. Strict 
aseptic precautions are necessary in order to keep out other infections. 
The rabbit should begin to show symptoms on the sixth or seventh day, 
and die on the ninth or tenth. Usually the rabbit is not allowed to 
die, l)ut is chloroformed on the last day in order to avoid terminal in- 
fections and unnecessary suffering. The spinal cord is removed and 
hung in a bottle containing potassium hydroxid. These bottles are 
kept in the dark at a temperature of 20°-22° C. Under these conditions 
the cord gradually desiccates, and at the same time the virulence of 
the virus diminishes. Tintil the fourteenth day, when it is no longer 
infective. This is why Pasteur started the treatment with a cord four- 
teen days old. 

One half a cubic centimeter of the cord constitutes a dose. This is 
ground in sterile salt solution so as to produce a uniform emulsion, which 
is injected into the subcutaneous tissue of the abdominal wall. In many 
institutes the small segments cut each day from the drying cord are 
placed in pure glycerin. The virulence of the cord in glycerin is not 
altered for at least 30 days, if kept in the dark and at 15° C. This 
method, introduced by Calmette, is very convenient, especially where 
comparatively few ])atients are treated. Glycerin has the added advan- 
tage of destroying infections due to non-spore-bearing bacteria that 
may be present. As a further precaution, bacteriological examinations 
are made of parts of the spinal cord in order to insure the absence of 
bacteria, and the rabbit is carefully autopsicd as a guarantee that no 
other disease is present. 

The scheme of treatment advocated by Pasteur and still used at 

I'Institut Pasteur in Paris and many other places is as follows: 

^N. Y. Med. Jour., Oct. 9, 1909, also Arch, of hit. Med., Sept., 1911, VIII, 
3, p. 353. 




Mild Treatment 

Intensive Treatment 




Age of 

the Dried 


Amount of 



1 cm. to 5 c. c. 

of th 

Age of 
e Dried 

Amount of 



1 cm. to 5 c. c. 

14 Days 

3 c. c. 


/ 14 Days 

3 c. c. 

























/ 10 


3 ■ 

' 6 
I 6 



































































































Many Pasteur institutes now use a modified treatment, starting with 
an 8-day instead of a 14-day-old cord, which is exemplified in the scheme 
on next page, used at the Hygienic Laboratory, Public Health Service. 

The Pasteur scheme has been further modified in various ways. 
Bujwid and Babes use stronger treatment than that advocated by Pas- 
teur. Puscariu in Jessy uses a method based upon the experiments of 
Babes, which show that an emulsion of fixed virus when heated to 50°- 
58° C. is attenuated in virulence. Tizzoni and Cattani attenuate the 
virus in gastric juice, and Hoyges simply dilutes the fresh virus. The 
original dilution is 1-100, and the first dose is one ten-thousandth of 
this. Ferran in Barcelona, Proescher in Pittsburgh, and others in- 
ject patients with the unaltered, fresh, fixed virus. • The advantages 
of using the virus as fresh and strong as possible are that an active im- 
munity is produced more quickly, and this is of considerable importance 
in wounds of the face; also in wolf and cat bites, which frequently 
have a short period of incubation. Further, only one or two injection^s. 




D. C. 


Age of the Dried 




Adult 5 to 10 Years 


1 to 5 Years 

Scheme for Mild Treatment 

1 i 


2.5 c. c. 

2.5 c. c. 

2.0 c. c. 

2 1 





3 ' 































































































Scheme for Intensive Treatment 



2.5 c.c. 

2.5 c.c. 

2.5 c.c. 



























































2 5 










































of the fresh vims are necessary to produce an immunity, and this 
shortens and simplifies the treatment very much. 


Harris ^ has shown that rabic material may be completely desiccated 
without destruction of virulence, provided the dehydration takes place 
at a low temperature. The lower the temperature the greater will be 
the amount of virulence preserved. Virus so desiccated contains per 
weight as much infectivity as the fresh virus. The loss of virulence 
of the dried virus is so slow that it may be standardized, permitting an 
accuracy of dosage hitherto impossible. The unit is the smallest amount 
which, when injected intracerebrally into a full-grown rabbit, will pro- 
duce paresis on the seventh day. The use of this desiccated virus in the 
prophylactic immunization of anim:.]s and persons offers many ad- 
vantages over other methods. 

Treatment at a distance from a Pasteur institute is now possible 
by sending a piece of cord, or the emulsion in glycerin. 

Care During the Treatment. — During the treatment the patient 
may go about his usual business. It is not necessary to stay in bed. 
The patient should, however, avoid fatigue, cold, and alcohol. It has 
been shown that these are important predisposing factors to the disease. 
It was found that customs' officers returning to the Siberian borders 
after prophylactic treatment for wolf bites showed an unusual mortal- 
ity, which seemed to be due to exposure to cold. The disease has been 
observed to be brought on after a cold bath, falling into the water, 
and similar depressing influences. 

Complications of the Treatment.- — The Pasteur prophylactic treat- 
ment may be complicated by (1) local reactions or (2) paralysis. 

Local reactions at the site of the wound are usually trivial. Ab- 
scesses almost never occur. The local reactions consist of redness and 
induration. Their occurrence increases with the progress of the treat- 
ment; they are most frequent in the second week. As the treatment in- 
volves the introduction of a large quantity of foreign proteins into 
the body, it is probable that these reactions represent a phase of hyper- 
susceptibility. (See Anaphylaxis.) 

Paralysis. — Paralysis occasionally occurs and may be fatal. There 
is doubt concerning the cause of this paralysis, and a question whether 
it may be a mild or modified type of rabies, or a form of anaphylaxis. 
In a case treated at the Hygienic Laboratory the paralysis came on 18 
days after treatment, and was transient. The New York Pasteur In- 
stitute reports a death from "ascending paralysis," which came on four 
days after the treatment. W. A. Jones - reported two cases with re- 
covery. In 1905 Eemlinger, head of the Constantinople Institute for 
Eabies, reported 40 cases of paralysis ; Mliller found 16 cases in the liter- 
ature, and had two of his own; Panpoukis, three cases; Jones, 2; mak- 
ing a total of 63, 2 of whom died. 

''Jour, of Infect. Bis., May, 1912, X, 3, pp. 369-377, 
?/pwr, 4. M. A., Nov. 13, 1909, p. 1626, 


The Immunity. — Dukation. — The immunity appears two weeks af- 
ter tlie treatment and lasts a varying period of time, depending upon 
the individual — at least for several years. In this respect it does not 
differ from other instances of acquired imnnmity. The fact that the 
immunity appears on about the fifteenth day after the end of the treat- 
ment was discovered by Pasteur as a result of animal experimentation. 
The statistics of the Pasteur Institute, giving the mortality from rabies 
in persons following the prophylactic treatment, exclude instances in 
which the disease develops within fifteen days after the end of the 

Nature. — The nature of the immunity is not clear. It certainly 
is not due to an antitoxin. Immune bodies are demonstrable in the 
blood twenty days after the last injection. This is determined by mixing 
in vitro the active virus with the blood serum, which neutralizes its 
activity. Tliis neutralization is generally considered to be microbicidal 
or lytic in nature. 

Degree. — The degree of the immunity also varies, as is evidenced 
by the fact that a certain small percentage of the persons treated die 
of rabies. 

The Results of the Treatment. — Statistics giving the results of the 
treatment are somewhat difficult to analyze, as many factors are unob- 
tainable. Patients should l)e kept under observation at least a year. 
Exceptional cases occur one year following the treatment. Cases that 
occur witliin fifteen days after the treatment are excluded from the 
French statistics, for reasons that have already been stated. The fig- 
ures on this basis show a mortality which averages about 0.5 per cent. 
Better results arc being obtained from year to year. 

The table on the following page gives the general results at Tlnstitut 
Pasteur, Paris, since beginning the treatment. 

When we compare these figures with the fact that from (5 to 10 per 
cent, and sometimes 16.6 per cent, of all persons bitten by rabid 
dogs die of rabies, the prophylactic value of the Pasteur treatment is 

Some series of cases give a much higher mortality. Thus, of 855 
cases collected by Tordieu, Thamehayn, and Bouley, 399 ended in death, 
or 46.6 per cent. In another series of cases given by Bouley, out of 
266 persons bitten by mad dogs, 152 died of hydrophobia. But of 
these 120 were bitten on the face and hands^ the greater danger of 
which has been mentioned. The mortality of bites from wolves is placed 
at from GO to 80 per cent. 

Contraindications. — There are no particular contraindications to the 
treatment. All ages and conditions should be treated if exposed. Ap- 
parently no harm is done pregnant women. I have injected patients 
having malaria without trouble following. The treatment may be con- 




































































































1909 ■ 




tinned in patients having colds, fevers, and other ailments without no- 
ticeable harm. 

When to Give the Pasteur Treatment. — It is sometimes dilhcult to 
decide whether the Pasteur ^prophylactic treatment should or should 
not be given. The treatment causes sufficient personal inconvenience, 
not to speak of the danger (however slight) of paralysis, to avoid ad- 
vising it if unnecessary. In many cases it is impossible to discover 
whether the dog which inflicted the bite is mad or not. The rule in 
cases of doubtful exposure is to advise the treatment. 

Persons not infrequently apply for advice giving the following his- 
tory": They have not been bitten, but they have been licked on the 
hands and face by a dog which subsequently developed the disease. 
Persons are sometimes similarly exposed by washing the mouth of a 
rabid horse. In these cases the important question is whether there 
were fissures or abrasions in the skin at the time. There may be little 
wounds in the skin not evident to the naked eye. In such cases the 
danger is slight, but in apprehensive subjects the assurance of protection 
which the treatment affords is an important element in arriving at a 

In all cases it is important to know whether the dog is mad or not. 
If the dog can be found and kept under observation for 10 days and 
no symptoms appear, the Pasteur treatment is not necessary. Animals 
killed early in the course of rabies may fail to show the miscroscopic 


evidence of the disease, thus causing an indefinite delay in diagnosis 
awaiting inoculation tests. Should symptoms develop, the question of 
diagnosis is all-important. 

Diagnosis of Rabies in Dogs. — The diagnosis of rabies in dogs may 
be made in three ways: (1) from the symptoms; (2) from the presence 
of Negri bodies in the central nervous system, and (3) by animal 

1. The syiiiptouis may be very suggestive, but a diagnosis must 
always rest upon the pathological lesions and the inoculation tests. 
The course of the disease may be divided into three stages: a pre- 
monitory stage, a stage of excitement, and a paralytic stage. The 
first two stages may be absent or transient. All rabid animals invariably 
become paralyzed before they die. In dogs the first symptom consists 
solely in a change in the disposition of the animal. He is easily ex- 
cited, but docs not show a disposition to bite. Soon the restlessness 
becomes more marked, and the animal may become furious and even 
show signs of delirium. The animal does not fear water, as is com- 
monly supposed, but rushes about attacking every object in his way. 
Dogs sufl'ering from furious rabies have a tendency to run long dis- 
tances (35 miles or more) often biting and inoculating large numbers 
of other animals and persons en route. Very soon paralysis sets in, 
commencing in the hind legs, and finally becomes general. The course 
of the disease is always rapid, averaging from 4 to 5 days, rarely exceed- 
ing 10 days. When the stage of excitement is brief or absent, the disease 
is known as dumb rabies. This is the prevailing type in Turkey. This 
explains the relative rarity of rabies in man in Turkey, where dogs 

2. There is a difference of opinion concerning the significance of 
the Negri bodies {Neuroryctes hydrophohioe) , which, however, are very 
constant in rabies and peculiar to it. If Negri bodies are found in 
the dog, the Pasteur treatment should be started at once. The absence 
of Negri bodies, however, does not necessarily mean the absence of 
rabies. These bodies are sometimes difficult to find, or may not be 
present in the parts of the central nervous system which are examined. 
Negri bodies for diagnostic purposes may best be demonstrated by im- 
pression preparations stained according to Van Gieson, as recommended 
by L. Frothingham; or smears stained by the Mallory eosin-metliylene- 
blue method recommended by Williams and Lowden. Smears are 
prepared by crushing a small portion of the brain matter between two 
slides; portions are selected from Ammon's horn and also from the 
cerebellum, cerebral cortex, and medulla. These smears are then fixed 
and stained as follows: 

(a) Zenker's solution for 15 minutes. 

(b) Wash in tap water. 


(c) Ninety-five per cent, alcohol tinted with iodin. 

(d) Absolute alcohol five minutes. 

(e) Five to ten per cent, watery solution of eosin (Griibler W. g.) 
five minutes. 

(f) Stain in Unna's polychrome methylene blue two to three min- 

(g) Wash in water. 

(h) Differentiate in ninety-five per cent, alcohol. 

(i) Blot off, dry, and examine with oil immersion lens. 

The lesions of Van Gehuchten and Nelis, described in 1900, are the 
most characteristic anatomical changes. These lesions are found in the 
peripheral ganglia of the cerebrospinal and sympathetic systems, espe- 
cially in the plexiform ganglia of the pneumogastric nerve, and also the 
Gasserian ganglia. The normal nerve cells of these ganglia lie in a 
capsule lined with a single layer of endothelial cells. In rabies these 
endothelial cells proliferate and the nerve cells are pushed aside and 
even destroyed. The ganglion may finally contain only round cells. 

3. The final diagnosis of rabies rests upon animal experimenta- 
tion. A small quantity of the suspected material is placed under the 
dura mater of a rabbit or guinea-pig. The diagnosis by this method, 
however, requires so much time (on acco^mt of the long period of in- 
cubation of the disease) that it is of no practical value in deciding 
whether or not the Pasteur prophylactic treatment should be given, but 
in any critical case the positive evidence furnished by animal experi- 
mentation is incontrovertible. 


As a danger to the public health, as a peril to the family, and as a 
menace to the vitality, health, and physical progress of the race, the 
venereal diseases are justly regarded as the greatest of modern plagues, 
and their prophylaxis the most pressing problem of preventive medicine 
that confronts us at the present day. 

There are three venereal diseases : syphilis, gonorrhea, and chancroid. 
In order to have a clear understanding of the problems of venereal 
prophylaxis it is necessary to have a knowledge of the essential features 
of these preventable infections. Two of them, syphilis and gonorrhea, 
are of great importance, because they are very prevalent and because 
they are very serious infections with grave consequences. 



Thero are many ptrikiiif; tilings almiit syphilis, but nothing so strik- 
ing as its persistence in spite of knowledge complete enough to stamp 
it out and in view of the popular dread in which the disease is held. 
It is prevental)le, even cural)lc — yet scarcely another disease equals it 
in the extent and intensity of its ravages. 

Syphilis is a good illustration of the fact that it is much more diffi- 
cult to control a disease transmitted directly from man to man than a 
disease transmitted hy an intermediate host, or one in which the infective 
principle is transferred through our environment. We have a certain 
amount of control over our surroundings, and we have dominion over 
the lower ani nulls, but the control of num requires the consent of the 

Civilization and syphilization have been close companions, hut syph- 
ilis is now less prevalent among civilized than uncivilized peoples — this 
is promising. Civilization, however, should not be content until it has 
controlled syphilis as effectively as it has a few other preventable in- 
fections. The effort to do so, at least, must be persistent and sincere. 

From the economic side, syphilis is not a serious disease in its pri- 
mary and secondary stages; that is, persons with syphilis during the 
early stages are usually not ill enough to cease work. Acutely fatal 
cases, such as frequently occurred in the sixteenth century, are now 
rare; in other words, the disease has lost much of its early virulence. 
It is the late numifestations, the sequelae and the so-called parasyph- 
ilitic lesions, as well as the inherited consequences of the disease, that 
cause great economic loss. About one-fifth of all the insane in our 
asylums are eases of general paresis ; 90 per cent, of these give the 
Wassermann reaction. Syphilis, alcohol, and heredity fill our insane 

The consequences of syphilis are often more severe upon the off- 
spring than upon the syphilitic parent. The infection itself, or various 
defects, especially of the nervous system, resulting from the consequences 
of syi)hilis, may l)e transmitted from parent to child, often with fatal 
results. When death does not ensue the results may be still more tragic. 

Syphilis is an infection caused by the Treponema pallidum (formerly 
known as the SpirocJiceta pallida). It is a communicable disease ac- 
quired by direct contact with infected persons or things. It runs a 
chronic course with local and general manifestations, usually divided 
into three stages, which are not always well defined. The primary 
stage consists of the chancre which forms at the site of the initial in- 
fection. The chancre is a hard indurated ulcer in the skin or mucous 
membrane, and appears about three weeks (not less than ten days) 


after the receipt of the infection. The secondary stage is characterized 
by a general invasion of the spirochete throughout the system, as in- 
dicated by a general involvement of the lymph nodes, eruptions upon the 
skin and mucous membranes, fever, anemia, and other indications of 
a generalized infection. The third stage is characterized by a localized 
granulomatous growth known as a gumma. Gummata may appear in 
almost any tissue or organ of the body. A fourth stage is sometimes 
added to the picture, consisting of the sequela or parasyphilitic phe- 
nomena, such as general paresis, arteriosclerosis, locomotor ataxia, an- 
eurysm, etc. 

The health officer should regard syphilis just as he does the acute 
febrile exanthematous diseases. Because syphilis runs a slow and often 
chronic course witli mild constitutional symptoms during its early 
stages, it is often placed in a class by itself. This is a mistake. Syph- 
ilis has its period of incubation, eruption, and decline, just as measles 
and smallpox have. 

There is no natural immunity to syphilis ; all are susceptible, hut the 
severity of individual cases varies greatly. This is due either to the 
virulence of the strain, the amount of the infection, or to variation in 
individual resistance. The disease is now much less severe than it was 
following the pandemic which spread over the civilized world after 1494, 
when the army of Charles VIII, 32,000 strong, started out to conquer 
the Italian peninsula. 

One attack of sj^philis confers an immunity, in that reinfections do 
not produce another chancre. , That is, the virus cannot be inoculated 
upon a person who has or has had the disease. The immunity is pe- 
culiar in that, while the person cannot have a second chancre, this fact 
has no influence upon the development of the secondary and tertiary 
lesions resulting from the first infection. For CoUes' and Profeta's 
laws of syphilitic immunity and the transmission of syphilis see 
page 447. 

In a large majority of all cases of syphilis the infection is trans- 
mitted during sexual approach. It is, therefore, spoken of as a venereal 
disease; many cases, however, are contracted out of venery. These ac- 
cidental infections are more common than is ordinarily supposed. 
Metchnikoff reports that a great number of cases of non-venereal syph- 
ilis occur among children in Eussia, where the peasants live huddled 
together and in ignorance. Syphilis may be passed from one person to 
another by kissing, and the danger is greater when there are mucous 
patches or other open lesions upon the mouth. The disease may also 
be transmitted in wounds inflicted by the teeth of syphilitics. In sur- 
gery and midwifery practice physicians are not infrequently infected 
through minute abrasions — a pin prick or a scratch from a scalpel is 
sufficient to introduce the virus. Midwifery chancres are usually upon 


the fingers. Chancre of the lip is the most common of the erratic or 
extragenital forms, and may be acquired in many ways apart from direct 
infection, such as the use of spoons, glasses, pipes, etc., which have 
recently been mouthed by a syphilitic. The virus may also be trans- 
mitted by towels, clothing, razors, handkerchiefs, surgical and dental 
instruments, human vaccine virus, etc. The list of articles that have 
conveyed the contagium is comprehensive. The Treponema pallidum is 
a fragile organism and soon dies upon fomites, but the infection is suffi- 
ciently prevalent and the danger sufficiently real to demand care. 
Chancres of the mouth and on the tonsils result, as a rule, from per- 
verted practices. Wet nurses are sometimes infected on the nipple, and 
it occasionally happens that the relatives of a syphilitic child are acci- 
dentally infected. The hereditary and congenital transmission of syph- 
ilis is discussed on page 446. 

Syphilis lowers the standard of health and paves the way for other 
diseases. Wliatever the etiological relationsliip may be, it is definitely 
known that syphilitics are prone to die early from affections of the heart 
and vessels, general paresis, diseases of the central nervous system (loco- 
motor ataxia), chronic nephritis, arteriosclerosis, aneurysm, etc. The 
actuaries of all life insurance companies know that the morbidity and 
mortality rates among syphilitics are very much higher than that of any 
other class of individuals of the community who enjoy apparent good 
health at the time of examination. 

ilost insurance companies refuse to accept syphilitics at all. Some 
companies require extra premiums to compensate for the extra risks; a 
few companies will accept exceptionally favorable cases who have had 
a thorough course of treatment, and who have shown no symptoms for 
3 to 5 years, but under these circumstances only special policies are 
contracted for which do not keep the applicant on the companies' books 
after 55 years of age. 

Syphilis was regarded as an infection peculiar to man until Xicolle 
and Hamonic in 1902, and Metchnikoff and Roux in 1903, transmitted 
the disease to the higher apes. As a result of these experiments cer- 
tain important facts in reference to prophylaxis were discovered. ^Metch- 
nikoff and Roux found that bichlorid of mercury, 1-2.000, applied one 
hour after inoculation, does not prevent the development of the pri- 
mary lesion in the monkey. This is probably due to the fact that the 
action of the bichlorid is limited to the surface; it lacks penetration 
owing to its well-known property of coagulating albumin. Other anti- 
septics were tested, but in a long series of experiments, carried out on 
chimpanzees, baboons, and Macacus monkeys, Metchnikoff and Roux 
showed that mercurial inunctions are most successful in preventing the 
development of the chancre. The mercurial inunctions may be made 
with metallic mercury, calomel, white precipitate (aramoniated mer- 


cur}^), or salicyl-arsenite of mercury. Calomel ointment appears to be 
the best, and is the one now generally used. It is rubbed up in lanolin 
in the proportions of 1 to 3 or 1 to 4. The ointment should be rubbed 
upon the place for 4 to 5 minutes and not later than 20 hours after 
the receipt of the infection. This will usually prevent the development 
of the disease. Excision, or destruction of the chancre with the actual 
cautery or with corrosive antiseptics does not influence the development 
of the disease. 


Gonorrhea is much more prevalent than syphilis, and common opin- 
ion regards it as a comparatively trivial infection, that is, "no worse 
than an ordinary cold." As a matter of fact, gonorrhea is one of the 
serious infectious diseases, and the gonococcus occupies a position of 
high rank among the virulent pathogenic microorganisms. From an 
economic and public health standpoint, gonorrhea does not fall very 
far short of syphilis in importance; in fact, some give it first place. 

The serious consequences of gonorrhea are: complications such as 
periurethral abscess, gonorrheal prostatitis in the male, and vaginitis, 
endocervicitis, and inflammation of the glands of Bartholini in the fe- 
male. Perhaps the most serious of all the sequelse of gonorrhea are 
those which result from the spread by direct continuity of tissues, such 
as inflammation of the Fallopian tube, and sometimes of the endomet- 
rium, the ovar}', or even the peritoneum. The gonococcus has been 
found in pure culture in cases of acute general peritonitis. Other in- 
flammations caused by the spread of the infection are cystitis, which 
sometimes extends upward through the ureters to the kidneys. 

The gonococcus sometimes invades the blood and produces a general 
septicemia and pyemia ; death may occur from acute endocarditis. Gon- 
orrheal arthritis is, in many respects, the most damaging, disabling, 
and serious of all the complications of gonorrhea. It may even follow 
ophthalmia neonatorum. It is more frequent in males than in females, 
but a gonorrheal arthritis of great intensity may occur in a newly mar- 
ried woman infected by an old gleet in her husband (Osier). The 
serious nature of gonorrheal complications in the eye will be considered 
separately under Ophthalmia Xeonatorum. Gynecologists tell us that 
the greater part of their practice is made up of the consequences of 

Sterility is one of the serious consecjuences of gonorrhea. This 
may be caused in the male through epididvmitis, which is a very com- 
mon complication, and in the female by salpingitis, which closes or ob- 
structs the Fallopian tube. Stricture of the urethra in the male is a 
frequent sequel. 


Gonorrhea is usually transmitted by sexual congress; however, ac- 
cidental or innocent infections are not infrequent. Paul Bendig ' reports 
the following instance : Of 40 girls sent for convalescence to a brine 
bath, 15 showed signs of gonorrhea after tlie return. The infection 
came from an eight-year-old girl, who apparently had been suffering 
from gonorrhea for several years, and was spread through indiscriminate 
batliing in one bath tub and the use of the same bath towel. 

Gonorrheal infections in children require special consideration. The 
frequency of such infections may be judged from the observations of 
Pollack, who reports 187 cases treated in the Woman's Venereal De- 
partment of Johns Hopkins Hospital during the year 1909.' Pollack 
estimates that 800 to 1,000 children are infected each year in Balti- 
more, and that the same proportion probably holds good for other cities. 
The cause of the frequent infection among children is in part the su- 
perstition that a person infected- with syphilis or gonorrhea may get 
rid of it by infecting another — especially a virgin. 

When gonorrhea enters a children's hospital or an infants' home it 
is prone to become epidemic and is very difficult to eradicate. The 
story of the infection in the Babies' Hospital, Xew York, for eleven 
years, as told by Holt,^ illustrates the singular obstinacy of the infec- 
tion. In spite of the greatest care and precaution, there were, in 1903, 
65 cases of vaginitis with 2 of ophthalmia and 12 of arthritis. In 
1904 there were 52 cases of vaginitis, only IG of which would have 
been recognized without the bacteriological examination. In all. in 
the eleven years, there were 273 cases of vaginitis; 6 with ophthalmia 
and 26 with arthritis. Holt urges isolation and prolonged quarantine 
as the only measures to combat successfully the disease (Osier). It is 
impossible to control such epidemics without bacteriological diagnosis. 

Chancroid is not discussed separately because its prevention is sim- 
ilar to the measures used against syphilis and gonorrliea. Chancroid 
sometimes directly results in severe, even fatal, results, but does not, as 
a rule, leave dangerous sequelae. 


The same principles apply to the prevention of the venereal diseases 
as apply to the prevention of other communicable diseases. The fight 
against venereal diseases, however, is especially complicated and difficult 
because of the close association with prostitution, the problems of sex 
hygiene, and alcoholism — in fact, the question pervades the woof and 

' M-iinchener med. Wochenschr., 1909, p. 1846. 
''Johns Hopkins Hospital Bulletin, May, 1909, p. 142. 
^ New York Med. Jour., March, 1905. 


warp of society. There are three primitive appetites of man — hunger, 
thirst, and the sexual appetite. The first two persist throughout life; 
the last comes on at puberty, grows stronger during adolescence, and 
wanes with age. Any program for the control of the venereal diseases 
or the hygiene of sex must take into account the fact that we are deal- 
ing with a primal, impulsive, and natural passion which is the greatest 
force for social good, when used in accordance with the laws of nature, 
but may result in dire consequences when these laws are transgressed. 
The venereal diseases are among the most widespread and universal of 
all human ills, and enter more largely in the making and marring of 
domestic happiness than any other disease known to man. The diffi- 
culties of the situation should not deter the health officer and all those 
who labor for social uplift, for there is no more pressing j^roblem in 
preventive medicine. 

Attitude. — Our attitude toward the venereal diseases is very incon- 
sistent. There is a natural aversion toward these afflictions. The sani- 
tarian should make no distinction between the venereal diseases and 
other epidemic diseases; he should regard the greatpox in the same 
light that he regards the smallpox. The principles for the control of 
syphilis and gonorrhea differ in no wise from those used to control 
smallpox, leprosy, tuberculosis, measles, diphtheria, etc. The health 
officer must not regard venereal disease as a punishment for sin and 
crime — the victim or culprit needs heljD and sympathy. The immediate 
problem is the prevention of further spread of the infection. A person 
afflicted with a venereal disease should be treated in the same humane 
spirit that actuates the physician in other diseases. Eurthermore, the 
interests of the community require that the patient be accorded the best 
possible care and attention. The usual attitude toward the venereal 
diseases may well startle us when we consider that in most of our large 
cities no hospital will take a case of syphilis or gonorrhea during the 
acute stages, when these diseases are especially communicable. Morrow 
holds that the notoriously inadequate provision made for the reception 
and treatment of venereal patients is a disgrace to our civilization. 
Formerly lepers were segregated in vile lazarettos and cases of smallpox 
isolated in horrible pest houses; now we have comfortable and congenial 
isolation wards or special sanatoria for these diseases. From the stand- 
point of prevention suitable hospital accommodations should be provided 
for the venereal diseases. 

Education. — Education in sex hygiene and the venereal peril accom- 
plishes a certain amount of good. It may be questioned how much a 
knowledge of the consequences will prevent some persons committing 
crime. However, the old-style innocence must be regarded as present- 
day ignorance. Every boy and girl, before reaching the age of pu- 
berty, should have a knowledge of sex, and every man and woman be- 


fore the marriageable age should he informed on tlie suhject of repro- 
duction and tlie dangers of venereal diseases. Superficial information 
is not true education. On the other hand, it is a mistake to dwell un- 
duly upon the subject, for in many instances the imagination and 
passion of youth are inflamed by simply calling attention to the sub- 
ject. One of the ol)jects of cducatiou is to avoid the dangers of sex 
impurities, and all agree that this may often best be accomplished by 
keeping the mind clean, that is, away from the subject. The education 
must, therefore, be clear, ])ointed, brief, and direct. The object of 
education is not alone to help the individual to help himself, l)ut to 
influence necessary legislation and concerted public action ; also to les- 
sen the influence of quacks. A simple knowledge of the facts is a suffi- 
cient deterrent for some; others may be influenced through fear of 
the consequences. 

In general, it may be said that the best plan of education in mat- 
ters sexual is to answer the questions of children upon the subject of 
maternity frankly and truthfully, but to offer them no information on 
the subject. The growing child at the age of puberty shoidd be offered 
a certain amount of information concerning unnatural habits and should 
study physiology, biology, especially botan}', and the facts of fertiliza- 
tion. At about the age of sixteen or eighteen girls as well as boys 
should be instructed as to the venereal peril. The pamphlets issued 
by the Committee on Sex Hygiene of the Massachusetts Association of 
Boards of Health are admirable. One circular is for young uu'n, an- 
other for young women, and a third for those having venereal disease. 

Some of the facts all young men should know are: that the true 
purpose of the sex function is reproduction and not s^ensual ])lcasure; 
that the testicles have a twofold function, (a) reproduction and (b) to 
supply force and energy to other organs of the body; that occasional 
seminal emissions at night are evidences of normal physiological activ- 
ity; that sexual intercourse is not essential to the preservation of virility; 
that chastity is compatible with health; and that the sex instinct in 
man may be controlled. 

The primary function of the testicles is to build the boy into the 
man. Castration in early life, as in the case of eunuchs, results in 
a loss of the internal secretion of the testicles and a failure in develop- 
ment of the secondary sexual characters which distinguish the male. 
There are an alteration in physical conformation and in the voice, lack 
of beard, development of the mamma, etc. — in other words, an ap- 
proach to the feminine type. Healthy sexuality stimulates the imagina- 
tion, sentiment, the esthetic sense, and the higher creative functions. 
Excesses or any influence which weakens the sexual system impair the 
will power, influence self-respect, and diminish mental force. Experi- 
ence shows that arduous physical and mental labor, even after maturity 


is attained, is best performed when the sex organs are not exercised; 
while sexual excess distinctly impairs muscular strength and mental 
efficiency. It is unwise to frighten boys by exaggerating the results of 
self-abuse, which is rather the effect and not the cause of idiocy, insanity, 
degeneracy, and other defects of the central nervous organization. Self- 
abuse is no worse in its effects than natural coitus, except for its influ- 
ence upon character. Both are alike harmful when indulged in to 

Eegistration of Cases.— It is not possible to control any communi- 
cable disease, especially one that is pandemic, such as syphilis or gonor- 
rhea, without a knowledge of the cases and deaths. It is perhaps even 
more imjoortant to collect morbidity and mortality statistics of the great- 
pox than it is of the smallpox. But the public registration of private 
disease at once defeats its own object. Compulsory methods have here- 
tofore failed, and little may be expected from voluntary registration. 
When we consider that in our country we have no means of knowing 
the amount and distribution of smallpox, except to a limited degree in 
the registration area (which is less than one-third of our domain), what 
can we expect from the registration of the closely guarded secrets of 
the underworld ? The public registratian of ophthalmia neonatorum is 
successful because this form of gonorrhea is so apparent and the con- 
sequences so immediate and serious. The difficulties, however, need not 
deter us, and registration should be attempted even though the returns 
are incomplete. A start should be made, and, though the returns 
will be only partial at first, a gradual improvement may be ex- 
pected. Every case known and properly cared for is a focus of infection 

Continence. — One of the important facts to teach boys is that con- 
tinence is compatible with health. The testicles are like the tear glands 
and the sweat glands, in that they do not atrophy with disuse. Ben- 
jamin Franklin taught, as many another man of influence believes to- 
day, that the exercise of the sexual functions is necessary for health. 
This is a mistake and has done much harm. 

The sex principle is universal in nature. It is the force behind 
the constructive and progressive processes of all life, from the color 
adaptations of birds and flowers to the highest leadership in men. Ee- 
production is only one of its many functions; and the man who as- 
sumes that the so-called physical desire that at times thrills him indi- 
cates a need of sexual intercourse is in danger of depleting and wasting 
from his life a chief source of physical and mental growth. 

The single standard for men and women must be insisted upon, and 
the parent or guardian is justified in demanding a clean bill of health 
of the 3"oung man who proposes marriage. The young man, in turn, is 
entitled to the same from his prospective father-in-law. One of the 


defects of our artiiicial civilization wliich leads to harm is the post- 
ponement of the marriage age. 

Carnal lust may be cooled and quelled bv hard work of the body, 
as well as attention to personal hygiene — hence, one of the great ad- 
vantages of athletic sports for growing young men. 

Personal Hygiene. — Idleness, stimulating food, overeating, impure 
thought.-, evil associates, and alcohol excite the passions and are the bed- 
fellows of the venereal diseases. Purity of mind and cleanliness of 
body are heljjful prophylactics. Physical exercise and an out-of-door life 
divert the mind and help the body; it is a good safety valve for the 
excess animalism of youth. 

The public should be taught the necessity for thorough daily cleans- 
ing of the external genitals in both sexes, even in children. The large 
number of secreting glands and the decomposition of their secretions 
are liable to induce irritation and even minute lesions which open 
portals to infection of all kinds. 

Alcohol. — The strongest indictment against alcohol is that it excites 
the passions and at the same time diminishes the will power. The fact 
that alcohol lowers moral tone does much more harm than all the 
cirrhotic livers, hardened arteries, shrunken kidneys, inflamed stomachs, 
and other lesions believed to be caused by its excessive use. 

Prostitution. — The regulation of prostitution by means of medical 
inspection has been tried and largely abandoned. In other words, it is 
a failure, for the reason that it makes vice easy and is, therefore, morally 
wrong. It gives a false sense of security and does not reach clandestine 
prostitution, which is the great source of the venereal diseases. Under 
certain limited conditions, such as in army encampments, where clan- 
destine prostitution can be eliminated, regulation has markedly dimin- 
ished the prevalence of venereal disease. 

The elimination of prostitution is bcA'ond the dream of even the 
theoretical reformer. Its control resolves itself into questions of per- 
sonal hygiene and public hygiene; it is inextricably mixed up with alco- 
holism, and, like the abuse of alcohol, the question may best be reached 
by that slower, surer process of improving the moral and physical fiber 
of man. 

Medical Prophylaxis. — In accordance with the researches of Metch- 
nikoff and IJoux a reasonably efficient prophylaxis against the venereal 
diseases is now possible. In the United States Navy the following 
method is employed : The entire penis is scrubbed with liquid soap and 
water for several minutes, and then washed well with a solution of 
mercuric bichlorid, 1 to 2,000 in strength. If there are any abrasions 
present, they are sprayed with hydrogen peroxid from a hand atomizer. 
The man is then placed in a sitting position, well forward in a chair 
in front of a convenient receptacle, and given two injections of a 10 


per cent, solution of argyrol. He is required to retain each injection 
in the urethra for five minutes. After taking the injections^ the entire 
penis is thoroughlj'- anointed with a 33 per cent, calomel ointment. He 
is told not to urinate for at least two hours, and to allow the ointment 
to remain on the penis for some hours. A temporary dressing is placed 
on the parts to protect his clothes. 

The measures which will prevent gonorrhea will not ward off syphilis, 
and vice versa. 

The results attending such prophylactic treatment are very good. 
Thus Ledbetter ^ reports that at Cavite, before medical prophylaxis 
was instituted, the percentage of venereal diseases of all classes among 
the men averaged from 25 to 30 per cent, annually, and at times even 
higher. The percentage of gonorrhea was reduced to 8 per cent, annu- 
ally, and this percentage included about 30 patients who did not report 
for treatment. Chancroid was reduced from 5 to 2 per cent., which 
included 2 patients not reporting for treatment. Syphilis has been re- 
duced from about 20 cases annually to one case for the entire year 
1910, and this patient did not report for proph5dactic treatment. The 
results speak for themselves and show the efficiency of the prophylactic 
measures if properly and thoroughly carried out. 

Holcomb and Gather - report the following as a result of treatment 
used by them in 3,268 persons in the U. S. Navy between May 1, 1910, 
and August 31, 1911. The experience is considered to be a fair index 
of the results of medical prophylaxis. The treatment used by them 
is as follows : ( 1 ) Wash the penis, head, shank, and under f renum with 
1-5,000 bichlorid of mercury solution with a cotton sponge. (2) Pass 
water. Take urethral injection of 2 per cent, protargol solution and 
hold to count 60. (3) Eub 50 per cent, calomel ointment well into 
foreskin, head, and shank of penis, with particular care about the fre- 
num. Treatment taken within eight hours after exposure in 1,385 
cases shows 19 infections, or but 1.37 per cent. In the interval of 
from eight to twelve hours after exposure in 741 cases shows 25 infec- 
tions, or 3.31 per cent. Between twelve and twent}"-four hours in 920 
cases shows -16 infections, or 5 per cent. Of the 56 cases of gonorrhea 
occurring in the first twenty-four-hour interval, 26 were recurrent cases; 
the remaining 30 were primary infections. 

The use of salvarsan early in syphilis will prevent the further spread 
of the infection. 

Segregation. — Theoretically, every case of syphilis or gonorrhea 
should be isolated until the danger of infection is passed. Practically, 

^Ledbetter, Eobert E., "Venereal Prophylaxis in the U. S. Xavy, " Jour. 
A. M. A., April 15, 1911, Vol. LVI, No. 15, p. 1098. 

= Holeomb, E. C, and Gather, D. C, U. S. N., "Study of 3,268 Venereal 
Prophylactic Treatments," Jour. A. M. A., Vol. LVIII, No. 5, Feb. 3, 1912, 
p. 368. 


however, segregation is impracticable except with a limited number of 
cases. With better and more attractive hospital facilities and free beds 
a certain amount of segregation may be accomplished voluntarily and 
humanely. An alert health officer can trace the source of infection in 
certain cases and induce the women responsible to take the salvarsan 
treatment in the case of syphilis, or to submit to hospital care in the 
case of gonorrhea or chancroid. 

Routine circumcision and a medical examination as a necessary pre- 
liminary to marriage are further liygienic reforms advocated. 

Finally, in considering venereal prophjdaxis, it should be remem- 
bered that these diseases are of great antiquity and seem likely to con- 
tinue indefinitely, that they already affect a large number of the popu- 
lation, and are spreading; that the existing means for the treatment 
of them among the poor is insufhcient ; that the common mode of 
propagation is irregular and illicit intercourse; that prostitution arose 
in response to the strongest instincts and passions in the human breast; 
and that prostitutes themselves need protection and have claims on 
the humanity of the law. 


Preventable blindness is considered in this jilace because the lar- 
gest single factor causing needless loss of eyesight is gonorrhea. Among 
the infectious eye troubles the most destructive is ophthalmia neona- 

There are 64,000 registered blind persons in the United States. 
Of these about 1-0 per cent, (between six and seven thousand) are 
blind as the result of ophthalmia neonatorum. From 25 to 30 per 
cent, of all the blind children in all the blind schools of this country 
owe their infliction to gonorrhea. It has been estimated that probably 
one-half of the blindness in the world is preventable. 

Emphasis upon the great harm done by ophthalmia neonatorum 
should not blind us to the fact that there are other causes of blindness 
and eye deterioration which are preventable; thus we have to consider 
the later pus infections, syphilis, sympathetic inflammations, indus- 
trial accidents, accidents at play, progressive nearsightedness caused 
by violation of ocular hygiene, and a variety of inflammatory condi- 
tions. Functional disturbances of vision (amaurosis) and atrophy of 
the optic nerve may be brought about by poisoning with lead, alcohol, 
tobacco, and other toxic substances. This form of dimness of vision, 
or even loss of sight, occurs rather frequently, and in many instances is 

Trachoma is a menace to the integrity of sight. It is an infection 


caused by a filterable virus.^ It flourishes best where sanitary conditions 
are worst. The disease is slow and insidious in its development. A mass 
of sago-like granulations gradually fills in the retrotarsal fold, thereby 
limiting the lid movements and leaving the eye half closed. The infec- 
tion is rubbed into the eye by roller towels, handkerchiefs, fingers, and 
other ways. When once established, the disease is chronic, and per- 
manent cures are doubtful. Trachoma is much more prevalent in the 
United States than ordinarily supposed. The public eye clinics of 
Chicago are filled with patients showing the resulting deformities. 
Wilder located a center in southern Illinois, and it has also been found 
in the mountains of Kentucky and Tennessee, while in Oklahoma it has 
become a public menace. It is more or less prevalent in the poorer 
sections of all the large centers. 

Trachoma is of such a serious nature that all immigrants arriving 
at our shores have their eyelids everted and conjunctivae examined for 
evidence of this infection. An alien with trachoma is deported and the 
steamship is liable to a fine of one hundred dollars for bringing every 
case of trachoma where it can be shown that the disease might have 
been recognized at the port of departure. 

Wood alcohol is one of the causes of blindness. As small a quan- 
tity as a teaspoonful has caused loss of vision. Wood alcohol is used 
as an adulterant, especially in liquors. The excessive use of tobacco 
also leads to dimness of vision. 

In New York State about 200 industrial accidents resulting in 
total blindness occur annually. Besides this, there is a large number 
of accidents occurring on railroads in construction work, and in the 
field and forest. Many of the accidents to the eyes occurring in fac- 
tories are preventable. The majority of such accidents are due to small 
flying particles. 

A material proportion of blindness is caused by accidents to chil- 
dren at play; sometimes the eyeball is torn by a buttonhook or pierced 
by a knife or awl ; or a scissors blade, used to untie a knot, slips. Some 
eyes have been injured by the crack of a whip, by a shot from an 
air-gun or toy pistol. Accidents also occur to the eyes from fireworks, 
especially on the Fourth of July. 


Ophthalmia neonatorum or inflammation of the eyes of the new- 
born includes all the inflammatory conditions of the conjunctiva that 
occur shortly after birth — usually before the end of the flrst month. 

^Bertarelli and Caechetto, Centr. fur BaM„ Orig., I Abt., Bd. XLVIII, 
1908, p. 432. 


The conjunctivae of tlie ne\\l)orn are peciiliarly liable to infections. This 
delicate membrane rapidly acquires an immunity of a high order. The 
gonococcus is usually the cause of severe conjunctivitis occurring in 
a baby a few days old. The gonococcus has been demonstrated in 65 
per cent, of all cases, mild and severe. 

Ophthalmia neonatorum is not always gonorrheal, but may be pro- 
duced by other virulent microorganisms or by irritating substances. 
The microorganisms other than the gonococcus that sometimes cause 
conjunctivitis during the early days of life are : streptococci, the menin- 
gococcus, the Koch-Week's bacillus, the pneumococcus, the diphtheria 
bacillus, and even staphylococci. These are relatively so rare that we 
may disregard their etiological significance for our present purpose. 
The diagnosis of gonorrheal ophthalmia may readily be made by simply 
examining a stained smear of the secretion. 

The infection commonly occurs during the passage of the child 
through the genital tract of the mother and usually just before deliv- 
ery. It is caused by the entrance of the vaginal secretion containing 
gonococci into the conjunctival sac. It may also be caused after de- 
livery by infected hands, towels, sponges, or other objects. 

The disease varies in severity; sometimes it is very mild, with slow 
onset and spontaneous recovery. Usually, however, it is severe and 
serious. The inflammation may extend from the conjunctiva to the 
cornea and invade the deeper structures of the eye. Corneal ulcers 
and opacity may result, with complete loss of vision. In a typical 
case both the ocular and palpebral conjunctivae are red and very much 
swollen; the eyelids and surrounding tissues are infiltrated and there 
is a thick, creamy, abundant secretion. 

There are many grades of mild inflammatory condition, which must 
not be mistaken for gonorrhea. At birth the eyelids are almost always 
glued together with the normal sticky secretions. It is common, too, 
for the lids to remain red and sticky for a day or so. The diagnosis 
may be made in a few minutes by a microscopic examination. 

Prevalence. — Kerr calls attention to the fact that there are no com- 
plete statistics showing the prevalence of ophthalmia neonatorum, and 
only an approximate idea can be had of the number of cases by study- 
ing the admissions to schools for the blind. A committee of the Brit- 
ish Medical Association found that more than one-third of those in 
blind schools of Great Britain owed their affliction to this disease.^ 

In the United States and Canada, in 1907, out of 224 admissions 
to 10 schools for the blind, 59, or 24.38 per cent., were blind as a re- 
sult of ophthalmia neonatorum;- and out of 351 admissions to certain 

* British Medical Journal, May 8, 1909. 
''Jour. A. M. A., May 23, 1909, p. 1745. 


schools in the United States and Canada in 1910, 84, or 23.9 per cent., 
were blind from this cause. ^ 


As a result of studies made of ophthalmia neonatorum in 10 man- 
ufacturing cities of Massachusetts, Greene has presented figures which 
show that the minimum morbidity rate for this disease was 6.4 per 
1,000 births. A more complete census made by him for the practice 
of 173 physicians in 9 cities revealed an average morbidity rate of 
10.8 per 1,000 births.^ 

It is estimated that the total annual loss from gonorrheal ophthalmia 
in the United States is seven million dollars, and that an amount of 
more than one million dollars annually is spent in partially caring for 
its victims. A blind child costs the community an excess of about 
$1,500 for its schooling. 

Prevention.— Crede^s Method. — Crede in 1881 introduced an effi- 
cient method of preventing ophthalmia neonatorum at the Lying-in 
Hospital at Leipzig, thereby connecting forever his name with the pre- 
vention of the disease and the subsequent saving of the sight of many 
infants. Crede's original method consisted simply in placing one or 
two drops of a 2 per cent, solution of silver nitrate in each conjunc- 
tival sac, as soon as practicable after the birth of the head. 

In order to prevent gonococcic as well as other infections of babies' 
eyes, the following procedure is recommended: During pregnancy 
women should be instructed to practice daily external cleansing with 
soap and water and a clean wash-cloth. In case of any irritating dis- 
charge or even profuse white discharge, a physician should at once be 

Immediately after labor the eyelids should be carefully cleaned with 
sterile absorbent cotton or gauze and a saturated solution of boracic 
acid. A separate pledget should be used for each eye and the lids 
washed from the nose outward until quite free of all mucus, blood, or 
meconium without opening the lids. Xext the lids should be separated 
and one or two drops of a one per cent, silver nitrate solution should be 
dropped into each eye, between the outer ends of the lids. The lids should 
be separated and elevated away from the eyeball so that a lake of silver 
nitrate solution may lie for one-half minute or longer between them, 
coming in contact with every portion of the conjunctival sac. One 
application only of the silver nitrate should be made, and ordinarily 
no further attention need be given to the eyes for several hours. Each 
time the child is bathed the eyes should first be wiped and cleaned with 
pledgets of sterile absorbent cotton wet with a saturated solution of 
boracic acid. 

"^lUd., July 1, 1911, p. 72. 

^Monograph Series of the American Association for Conservation of Vision, 
Vol. I, No. 1. 


Crede used a 2 per cent, solution of silver nitrate, but, as this is 
sometimes irritating, a 1 per cent, solution is now commonly employed, 
and seems to afford equally efficient prophylaxis. The silver nitrate 
solution should be instilled into each conjunctival sac but once. Re- 
peated applications may cause serious inflammations. In fact, a single 
treatment sometimes causes a conjunctivitis, known as "silver catarrh," 
Because of the silver catarrh the strength of the silver nitrate solution 
has not only been reduced from a 2 to a 1 per cent, solution, but this 
may be neutralized after instillation with salt solution. Other prophy- 
lactic substances have been proposed. The best substitutes are a few 
drops of the newer silver compounds, as argyrol (25 per cent.) or 
protargol (5 per cent.). The following have also been recommended: 
Bichlorid of mercur}% 1-2,000 or 1-5,000, silver acetate, 0.23 per cent., 
recommended by Zweifel, who used it in 5,222 cases. Schmidt and 
Rimpler recommend aqua chlorini. Carbolic acid (1 per cent.) or other 
antiseptics have also been tried. No substance, however, is known to 
be as relial)le as silver nitrate, which should be used in all cases where 
there is any reason for believing that the mother is infected witli the 

If a conjunctivitis is present, a bacteriological examination of the 
discharge should at once be made. If the inflammation is due to the 
gonococcus a 2 per cent, silver nitrate solution should be used. In cer- 
tain mild, non-gonorrheal infection 0.5 per cent, is usually sufficient. 
If the Klebs-Loeffler bacillus is found, diphtheria antitoxin should be 
given without delay. If the diplococcus is present, a weak solution 
(1 grain to the ounce) of zinc sulphate should be instilled frequently. 

As a general rule, it is advisable to use a prophylactic as a mat- 
ter of routine in hospital and private practice. To use Crede's method 
upon every case necessitates the unpleasant suspicion that every woman 
is a possible source of gonococcus infection. If statements of the father 
about his previous life can be relied upon, an eye prophylactic can be 
safely omitted. In his private work Williams uses a boric acid solution 
except where there is special reason for believing that the mother has 
gonorrhea. The responsibility for risking the baby's eyes rests upon 
the medical attendant. There can only be one safe rule in case of 
doubt. It should be remembered that gonococcic infections of the con- 
junctiva occur in about one to every two hundred births (Edgar). 

The good results of Crede's method are sufficiently convincing to 
justify criminal proceedings upon those who fail to apply this simple 
prophylactic. Haab reduced the frequency of ophthalmia neonatorum 
in hospital practice from 9 to 1 per cent., while the statistics of many 
hospitals show only a very small fraction of 1 per cent. Stephenson's 
results are typical. In 2,265 births, ophthalmia neonatorum developed 
in 10 per cent, of the cases preceding the use of Crede's method. In 


1,160 births after this method only 0.17 per cent, developed any 
trouble. A small number of cases may develop despite the use of 
silver nitrate. 

The technique of applying the nitrate of silver is very important, 
for, in the opinion of Edgar, when ophthalmia neonatorum develops 
after the use of nitrate of silver, it is due either to a secondary infec- 
tion or to the fact that the solution does not really bathe the mucous 
membranes, but remains upon the lashes. The lids must be everted 
and the silver solution placed in the conjunctival sac either from a 
glass rod or a pipette. Care must be taken not to touch or injure the 
delicate membrane. 

Crede's method does not strike at the root of the evil. It would, 
of course, be much better to eradicate gonorrhea from men and women 
than to be compelled to drop silver nitrate into babies' eyes. Wrapped 
up with the question of ophthalmia neonatorum is the question of 
midwives, for to prevent blindness we must have intelligent and con- 
scientious obstetrical attendants, especially for the poor and ignorant 
classes. Midwifery practice needs regulation, supervision, and eleva- 
tion. Education is one of the bulwarks of prevention in this as well 
as other preventable infections. 

Legislation. — Ophthalmia neonatorum is an instance in which "the 
protection of the citizen from the assaults of ignorance, indifference, 
or neglect, when they threaten his well-being and even his economic 
efficiency, is a duty which the state cannot evade and which he has a 
right to exact." 

Laws for the prevention of the blindness of newborn infants are 
making progress slowly. Among the states in which the disease is 
notifiable are Connecticut, Massachusetts, Minnesota, Nebraska, New 
York, Oregon, South Carolina, Utah, Vermont, and Wisconsin. In 
some states the nurse, midwife, or parent is required to report the dis- 
ease, in other states the attending physician. 

Maine was the first state to take legal steps in 1891 to control 
ophthalmia neonatorum. In 1892 New York followed, with an amend- 
ment to the law relative to midwives and nurses. Subsequently most 
of the other states took legislative action.^ The provisions of the several 
laws are quite varied. In all of them, however, the object is to insure 
early treatment, and to this end compulsory notification is generally 
required. The health authorities of Massachusetts, New Jersey, 
Vermont, Ehode Island, New York, and the District of Columbia 
furnish prophylactic outfits to physicians. The outfit ordinarily 
consists of a small vial containing a 1 per cent, solution of nitrate 

^ Kerr, J. W., "Ophthalmia Neonatorum: An Analysis of the Laws and Reg- 
ulations Relating Thereto in Force in the United States," Public Health Bull. 
No. 49, U. S. P. H. & M. H. S., Oct., 1911. 


of silver, a sterilized dropper and hull), and a circular of instruc- 

In order to make material progress against ophthalmia neonatorum, 
as well as against infant mortality, it is essential that laws require 
prompt report of all hirths; it is the duty of the health authorities to 
see to it that such laws are effectively carried out.^ 


Compared with the major plagues of man, lockjaw has always been 
a rare disease. It is on account of the characteristic and fatal spasms 
that it early attracted attention. The student Avill be well repaid by 
a study of the historical development of the theories that have been 
advanced since the time of Hippocrates to explain the cause of tetanus. 
These theories mirror the prevailing thought upon the nature of dis- 
ease as it developed from that of evil spirits, through the humoral 
theory, the realm of miasms and noxious effluvia, to the germ theory. 
Tetanus could not escape the rheumatism theory which has been such 
an alluring catchall for symptoms and diseases difficult of explanation. 
"Taking cold" was assigned its usual role here as elsewhere. When no 
assignable cause seemed at hand, the disease was given the learned 
title— id iojiathic tetanus. 

Etiology. — In 1889, with the aid of anaerobic technique, Kitasato * 
for the first time grew the tetanus bacillus in pure culture, and by 

* The Massachusetts law reads as follows: 

Section 49. . . . Shouid one or both eyes of an infant become in- 
flamed, swollen and red, and show an unnatural discharge at any time vnih- 
in two weeks after its birth, it shall be the duty of the nurse, relative, or 
other attendant ha\4ng charge of such an infant to report in writinc: within 
six hours thereafter, to the board of health of a city or town in which the 
parents of the infant reside, the fact that such inflammation, swelling, and 
redness of the eyes and unnatural discharge exist. On receipt of such re- 
port, or of notice of the same s;\anptoms given by a physician as provided 
by the following section, the board of health shall take such immediate 
action as it may deem necessary in order that blindness may be prevented. 
Whoever violates the provisions of this section shall be punished by 
a fine of not more than one hundred dollars. 

Section 50. ... If a physician knows that ... if one or both 
eyes of an infant whom or whose mother he is called to visit become in- 
flamed, swollen, and red, and show an unnatural discharge within two weeks 
after birth of such infant, he shall immediately give notice thereof in writ- 
ing over his own signature to the selectmen or board of health of the town; 


OFFENCE. (Revised Laws, Chapter 75.) 
^Zeitschr. f. Eyg., Vol. VII, 18S9, p. 225. 


successfiTl inoculation experiments proved that this hacilliis was the real 
cause of tetanus. Kitasato further showed that the tetanus bacillus is 
not found in the heart's bloody of mice dead of tetanus, and therefore 
concluded that we are dealing with an intoxication, and not an infec- 
tion. We now regard tetanus as a type of the true toxemias. This 
work of Kitasato's was one of great importance, and led up to the epoch- 
making discovery of Behring and Kitasato ^ in the following 3-ear (1890) 
upon tetanus and diphtheria toxines and antitoxins, laying the founda- 
tion of serum therapy. 

Tetanus may be regarded almost solely as a wound complication. 
All wounds are not equally liable to this complication, even though 
tetanus spores are present. Punctured, lacerated, and contused wounds 
are much more susceptible to tetanus than cleancut or superficial wounds. 
The size of the wound is of much less consequence than its character. 
Fatal tetanus may develop from trivial wounds, such as pin scratches, 
small splinters, insect bites, vaccinations, etc. 

S3'mbiosis is an important factor in tetanus. Wounds infected with 
pyogenic organisms and other bacteria favor anaerobic conditions and 
permit the tetanus spores to germinate, and seem to encourage the 
growth of the bacillus and the development of toxine.- A few tetanus 
spores free of tetanus toxin in a clean wound may be taken care of by 
the phagocytic cells. This may readily be demonstrated experimentally 
by injecting animals with tetanus spores washed free of toxine. 

The normal habitat of tetanus is in the intestinal tract of herbiv- 
orous animals. Sanchez, Toledo, and Veillon ^ found tetanus in the 
feces of 4 out of 6 horses and in the feces of 1 of 2 cows. Park found 
tetanus bacilli in the intestines of about 15 per cent, of horses and 
calves living in the vicinity of New York City. They are present to 
a somewhat less extent in the intestines of other animals and of man. 

It is rather a curious paradox that the horse, which is the most 
susceptible of all animals to tetanus toxin, is one of the principal hosts 
of the tetanus bacillus. 

The spores taken in the food are not affected by gastric digestion, 
and in the small intestines find ideal anaerobic conditions, food supply 
and temperature for growth and development. Here they very prob- 
ably multiply and pass in the dejecta to pollute the soil. The soil, 
therefore, in all regions inhabited by nnan and domestic animals is 
more or less contaminated with tetanus. The bacilli, however, do not 
multiply in the soil. While the soil acts only as a vehicle, it is the 
immediate source of the large proportion of tetanus spores. 

^ Deutsch. med. Wochens., Vol. XVI, No. 40, p. 1113. 

- In the laboratory some of the strongest tetanus toxins have been prepared 
from mixed or contaminated cultures. 
^ La Semaine Med., 1890, X, p. 45. 


It is assumed, but not proven, that tetanus bacilli grow in tlie in- 
testinal tract of herbivora. It is conceivable that the spores simply pass 
tlirouiih the intestines without multiplying at all, but it is known that 
tetanus is capable of multiplying in symbiotic relation with otlier bac- 
teria wherever protein matter undergoes ])utrefaction under anaerobic 

On account of the great resistance of the spores, they are blown about 
in dust and are spread everywhere by dirt and manure. Tetanus 
has been found in hay dust, on horses' hair, in the dust of houses, bar- 
racks, and hospitals, in the mortar of old masonry, in street dust, in 
gelatin, and in the greatest variety of places. 

One of the agencies in the distribution of tetanus spores over 
limited areas is undoubtedly the common house fly. The arrow heads 
of certain savages in the Kew Hebrides contain tetanus spores obtained 
by smearing the arrowheads with dirt from crab holes in the swamps 
(Le Dantic). 

Tetanus bacilli are not equally numerous in all localities. The in- 
fection is much more prevalent in warm than in cold countries. It is 
especially severe in the tropics, yet Iceland at one time suffered severely 
from tetanus neonatorum. Some parts of Long Island and New Jer- 
sey have become noticeable for the number of cases of tetanus caused 
by small wounds. Tetanus spores are widely disseminated in India. 
Goodrich states that in Bombay alone there were 1,955 cases of tetanus 
in five years. These do not include the puerperal cases. 

Tetanus occurs either sporadically or in epidemic form. Formerly 
epidemics in hospitals (especially in lying-in' hospitals) and in wars 
were rather common. Before the days of antisepsis the infection was 
readily spread through instruments, fingers, bandages, etc. 

Trismus neonatorum , or tetanus of the newborn, was a common and 
very fatal infection, especially in the tropics. Before the days of 
asepsis the infection was permitted to enter through the umbilical 
wound. In certain of the West Indian islands more than one^half of 
the mortality among the negro children has been due to this cause. 
Since the introduction of proper methods of treating the cord the 
disease is rare. 

The wounds produced by blank cartridges are especially liable to 
develop tetanus. The source of the tetanus spore in these cases is not 
entirely clear. Wells examined 200 cartridges from five firms without 
finding the tetanus bacillus. It is probable that the spore is upon the 
skin and is carried along with the paper and powder from the blank 
cartridge. The peculiar character of the wound favors the develop- 
ment of tetanus. 

The great decrease in the number of cases of tetanus following 
Fourth of July wounds is due to the vigorous campaign carried on 


by the American Medical Association. In 1903 there were 406 deaths 
from tetanus; in 1904, 91; 1905, 87; 1906, 75; 1907, 73; 1908, 76; 
and in 1911 only 18 cases and 10 deaths. Eighty per cent, of these 
followed blank cartridge wounds. The good results are attributed 
to the more thorough and careful treatment of the wounds and especially 
the use of tetanus antitoxin as a prophylactic — and more recently to 
safer and saner methods of celebration. 

Tetanus spores or toxine may contaminate bacterial vaccines, anti- 
toxic sera, vaccine virus, and other biologic products used in human 
therapy. The possible association of tetanus with bacterial vaccines was 
demonstrated in the unfortunate outbreak at Mulkowal, India, in 1902.^ 
One hundred and seven persons were inoculated with Haifkine's plague 
prophylactic. Of these 19 were affected with symptoms of tetanus and 
died. In this case the tetanus probably grew as a contamination in the 
plague culture, for it is now well known that the anaerobic conditions 
produced in B. diplitherice , B. pesfis, B. siibUlis, and other organisms in 
liquid culture media favor the growth of tetanus and the development 
of its toxin. 

In St. Louis (1901) diphtheria antitoxin was taken from a horse 
during the period of incubation of tetanus and used in amounts from 
5 to 10 c. c. upon 7 children, all of whom died of tetanus. Bolton, 
Fiseh, and Walden - found that the serum was sterile, but contained 
tetanus toxin in considerable amount. If the serum had first been 
tested upon animals, its poisonous properties would have been discov- 
ered. This test is now required by the United States law of July 1, 
1902, for all serums and vaccines sold in interstate traffic. As a fur- 
ther precaution against this complication horses undergoing treatment 
for the production of immune sera are given prophylactic doses of te- 
tanus antitoxin from time to time. 

Tetanus sometimes occurs as a complication of vaccination. It is 
not clear in these cases whether the tetanus spores are contained in 
the vaccine virus or subsequently enter the wound. In many hundreds 
of special examinations made in the Hygienic Laboratory at Washing- 
ton tetanus spores have not been found in a single vaccine virus. Ex- 
periments show that in vaccine virus purposely contaminated the te- 
tanus spores remain alive and active for a long time (see page 19). 

It is, of course, not the rust on a nail that is dangerous, so far as 
tetanus is concerned, but the spore-bearing dirt it carries into the deep, 
contused wound that causes the trouble. Ge]atin may contain tetanus 
spores, and the subcutaneous injection of imperfectly sterilized gelatin 
as a hemostatic has sometimes resulted in accidents. 

''Jour. Trop. Med. and Hyg., 1907, X, p.' 33. 

^Bolton, Fisch, and Walden in St. Louis Medical Beview, Vol. XLIV, No. 
21, Nov. 23, 1910, p. 361. 



Tetanus is harmless \vlien taken 1)}' tlie mnntl). Susceptible animals 
may be given enormous doses of tetanus toxine hy the mouth without 
producing the disease. The l)acillus and its spore may be regarded as 
a saprophyte in the intestinal tract. There is, however, a suspicion 
that tetanus spores sometimes invade the organism through small wounds 
in the digestive or res])iratory tract. Perhaps some of the cases follow- 
ing surgical operations may be accounted for in this way rather than 
by infection of the catgut used for ligatures. 

Tetanus sometimes occurs in which no wound can be found. This 
is the so-called "idiopathic or rheumatic tetanus." One ex{)lanation 
of these eases is to be found in the fact that the spores are numerous 
in street dust and may enter the reP]uratory tract. They cannot do 
harm so long as the mucous membrane is healthy, but may enter through 
inflamed membranes or through small wounds in the nose. Tetanus 
bacilli have been found in the bronchial mucus of idiopathic eases. Tet- 
anus spores have recently been found in the lymph glands, liver, and 
other parts of the body, upsetting our previous view that they are strictly 
confined to the site of the wound. These spores may remain latent for 
a long time, awaiting favorable conditions to grow and produce toxin, 
thus giving another plausible explanation of some cases of idiopathic 

Incubation.' — The period of incubation in man is usually from 6 to 
14 days. The period is directly proportional to the amount of toxin and 
the severity of the disease. This can readily bo demonstrated ujion 
susceptible animals. In a study of 600 serial tests, Rosenau and Ander- 
son found this direct relation between the period of incubation and the 
severity of symptoms by the subcutaneous injection of varying amounts 
of toxin into guinea-pigs. Thus, guinea-pigs that showed symptoms on 
the third day usually died, a very small percentage recovering. The 
smaller the dose the longer the onset of symptoms is delayed, the 
milder is the disease, and the greater the chances of recovery. With a 
short period of incubation, 6 days or less, the disease in man is almost 
invariably fatal. With longer periods the disease is milder and recovery 
frequently takes place without the use of antitoxin or other measures. 
Tetanus toxin travels up the axis cylinders of the nerves to the cord 
and brain. It is also distril)uted in the blood. The period of incuba- 
tion, therefore, depends somewhat upon the point of entrance of the 
poison and its proximity to large motor nerve endings. 

Resistance. — The tetanus bacillus is readily destroyed by all the or- 
dinary agencies that kill spore-free bacteria. It is killed almost at once 
in contact with the free oxygen of the air. On the other hand, few, 
if any, forms of life have a greater resistance than the tetanus spore. 
Hours of exposure to 60° or 70° C. do not affect them. They usually 
survive an exposure of one hour to 80° C, but, as a rule, are killed in 


streaming steam or boiling water in 60 minutes. Tetanus spores, how- 
ever, vary greatly in the power to resist the boiling temperature. Kita- 
sato ^ found them to resist 80° C. for one hour, but to be killed in 
streaming steam in 5 minutes. Vaillard and Vincent ^ found that the 
spores heated in the presence of moisture in a closed vessel would resist 
destruction at 80° C. for 6 hours, at 90° C. for 2 hours, and 100° C. 
3 to 4 minutes, that they were not always destroyed in 5 minutes, but 
never resisted more than 8 minute? at 100° C. Levy and Bruns^ found 
that destruction begins at 8^^ minutes at 100° C; after 15 minutes 
few survive, after 30 minutes none. Falcioni ^ studied the subject in 
view of the dangers of the subcutaneous injection of gelatin. He im- 
pregnated gelatin with spores of tetanus bacilli grown in agar or broth 
for 10 or 13 days, and used Koch's steam sterilization. He found the 
spores to resist destruction for 2%:. I^^^t not for 3, hours in streaming 

The experimental results are, therefore, sufficiently varied and con- 
flicting to suggest that races of tetanus bacilli exist, the spores of which 
vary widely in their resistance to moist heat at 100° C. Theobald 
Smith ^ found that under certain conditions of cultivation some tetanus 
spores survive a single boiling or streaming steam for 20 minutes reg- 
ularly, usually for 40 minutes, and occasionally for 60 minutes; in one 
case 70 minutes' exposure did not destroy the spores. He also showed 
the possibility of tetanus spores surviving in culture fluids sterilized by 
discontinuous boiling or steaming in routine laboratory work for fully 
20 minutes on three successive days. 

Tetanus spores resist the action of 5 per cent, carbolic acid for 10 
hours, but are killed in 15 hours. A 5 per cent, solution of carbolic 
acid, however, to which 0.5 per cent, of hydrochloric acid has been 
added, destroys them in 2 hours. Bichlorid of mercury, 1-1,000, kills 
the spores in 3 hours, and in 30 minutes when 0.5 per cent, of hydro- 
chloric acid is added to the solution. According to Park, silver nitrate 
solution destroys the spores of average resistance in 1 minute in 1 per 
cent, solution, and in about 5 minutes in a 1 to 1,000 solution. Tetanus 
spores are destroyed with certainty when exposed to dry heat at or 
above 160° C. for one hour, or to steam at 120° C. for 20 minutes. En- 
tire confidence may be placed upon either of these two methods. 

Direct sunlight does not kill the spores, but seems to diminish their 
virulence. Under certain circumstances they may live a very long time; 
Henrijean reports that, by means of a splinter of wood which once 

^Zeitschr. f. Byg., VII, p. 225. 

^ Annales de I'lnstitut Pasteur, 1891, V, p. 1. 

^Grensgeb. d. Med. u. Chir., 1902, X, p. 235. 

* Annali d'igiene sperimentale, 1904, N. S., XIV, p. 319. 

' Jour. A. M. A., March 21, 1908, Vol. L, pp. 929-934. 


caused tetanus, he was able after 11 years again to cause the disease 
I)v inoculating an animal with the infective material. 

Prophylaxis. — Local Tredlijicnt of Wounds. — Wounds, however in- 
significant, should be thoroughly cleansed. Punctured or lacerated 
wounds in which there is special danger of tetanus shoidd be freely 
opened, and every particle of foreign matter carefully removed. Prompt- 
ness in cleansing the wcnmd surgically is almost as important as thor- 
oughness. Wounds containing garden earth, street dust, or other mate- 
rial liable to contain tetanus spores sho\dd receive special consideration. 
After laying open and thoroughly cleansing siich wounds, it may be ad- 
visable to disinfect them with the actual cautery or strong chemical 
agents. For this purpose carbolic acid (from 25 per cent, to pure) or a 
strong solution of formalin may be used. Silver nitrate destroys the tet- 
anus spores in laboratory experiments, but lacks penetration in the pres- 
ence of albuMiinous matter. It is sometimes good practice to totally excise 
the wound, and even amputation must be considered in certain eases. 
The division of the und)ilical cord and the treatment of the navel in the 
newborn must be done under the strictest asepsis. All wounds in which 
there is any suspicion of tetanus should be kept open and freely drained, 
and otherwise treated so as to discourage anaeroljic conditions. 

Tetanus spores gain entrance into wounds not only from manure, 
garden soil, street dust, and similar sources, but also from the hands, 
instruments, bandages, suture material, or other objects. It is impor- 
tant to remember that the tetanus spiu-e is exceedingly resistant to heat 
and chemical agents, and that in surgical and obstetrical practice con- 
fidence should not be placed simply upon boiling to destroy the spores. 
Very particular care must be exercised in the disinfection of substances 
injected into the body, such as gelatin and other organic materials. 
For the destruction of tetanus spores complete confidence may be placed 
in the autoclave, in which a temperature of 120° C. for 20 minutes is 
attained, or exposure to dry heat at 160° C. for 1 hour. 

It should be remembered that tetanus toxin is manufactured in the 
wound and is thence transported mainly along the nerve roots to the 
spinal cord and brain. It is therefore important to destroy or neutral- 
ize the toxin in the wound. For this purpose dry tetanus antitoxin may 
be dusted upon the wound. Formaldehyde, even in comparatively weak 
solutions, destroys the activity of tetanus toxin. 

Specific Prophylaxis. — Tetanus antitoxin is a specific and trustworthy 
preventive. Its use, however, must be understood to achieve satisfactory 
results. The antitoxin must be administered before the advent of 
symptoms, for after the tetanus toxin has combined with the motor 
nerve cells in the central nervous system it can neither be displaced nor 
neutralized with antitoxin. In such cases the most that the antitoxin 
can do is to combine with and neutralize the free toxin and thus pre- 


vent. further damage. This in itself is quite worth while in the treat- 
ment of tetanus. At least 1,500 units of tetanus antitoxin should be 
given as a prophjdactic dose.^ It is important to remember that the 
tetanus antitoxin is eliminated or otherwise disposed of in the body 
in the course of 10 days or 2 weeks. Therefore, in cases in which the 
wound does not heal well, as a result of mixed infection, or for other 
reasons, it is desirable to repeat the injection. This may be done at 
intervals as long as the danger persists. Occasionally tetanus bacilli 
persist in the i^us-infected tissues, and, when the injected antitoxin has 
been exhausted, there may occur a late development of tetanus. Kowan ^ 
reports a fatal case of tetanus in spite of the prophylactic use of 2,000 
units of antitetanic serum, given 5 hours after the accident. In this 
case, however, the symptoms appeared 25 days later. The wound in 
this case was a compound fracture with a free discharge of rather 
foul-smelling pus. Instances in which 1,500 units of tetanus antitoxin 
have failed to prevent the development of tetanus in this country are 
rare. The few failures in France and Germany may be attributed to the 
fact that in those countries it is customary to use a smaller amount or 
a less potent serum than is used in this country. 

Wounds produced by blank cartridges and other Fourth of July 
accidents should always be regarded as suspicious, and should be given 
careful local treatment, supplemented with a prophylactic injection of 
antitoxin. The prevention of tetanus complication of vaccine wounds 
consists in : 

1. The use of a reliable vaccine which has been biologically tested 
in accordance with the federal act. 

2. Proper methods of vaccination to avoid unnecessary scabs and 
anaerobic wound conditions. 

3. Surgical asepsis of the operation and after-treatment. 

Tetanus and other wound infections may be avoided, in those ex- 
posed to accidents, by cleanliness of body and clothing. A bath before 
a battle is a reasonable protection said to be adopted in the Japanese 
Army and Navy. The common experience of mankind teaches him 
that most wounds heal without tetanus, and that tetanus is, in fact, 
a relatively rare infection. The physician, however, is in no case jus- 
tified in taking chances, and it is one of the duties of the medical pro- 
fession to teach the public that it pays to thoroughly cleanse and care 
for wounds, however trivial, at once, and in accordance with modern 

^As soon as symptoms appear 20,000 units or more of tetanus antitoxin 
should be introduced directly into the circulation by intravenous injection; some 
antitoxin may also be injected into the nerves leading from the wound. In 
tetanus, as in diphtheria, time is the important element. A few units introduced 
early are worth more than thousands late. 

■"Jour, A. M. A., XIV, No. 7, Feb. 12, 1910, p. 533. 




Typlioid fever is a sanitary problem of first magnitude, especially 
in this country, where it is unduly prevalent. In the United States 
typhoid fever stands fourth on tlie list of mortality tables : tuberculosis 
comes first, then pneumonia, cancer, and typhoid fever. The aver- 
age fatality from typhoid fever being nearly 10 per cent., it would, 
therefore, take still higher rank on the morbidity tables. In 1910 
there were 25,000 deaths from typhoid fever in the United States, 
representing at least 250,000 cases. 

Our general attitude toward typhoid fever is inconsistent; familiar- 
ity has bred a remarkable indifference to the disease. Every case of 
typhoid fever means a short circuit between the alvine discharges of 
one person and the mouth of another. The physician has a dual duty 
in the care of a case of typhoid fever: one is to assist the patient, 
the other is to protect the community. On the other hand, the people 
should learn the lesson that a case of typhoid fever should be regarded 
as seriously as a case of cholera. These two diseases present many 
features in common. Both are intestinal infections of bacterial na- 
ture; in both diseases the alvine discharges contain the microorgan- 
isms which reinfect another person when taken by the mouth. Both 
diseases prevail especially in hot weather, both diseases are peculiar 
to man, so that the patient is the fountainhead of each infection. 
Water, food, fingers, and flies play a similar role in both instances. 
In the case of cholera the dread of the disease is an important factor 
in keeping it out of the country or in preventing its spread when once 
introduced. By strange contrast, there is a remarkable indifference 
to typhoid fever. A wholesome fear of typhoid fever would materially 
assist the health authorities in combating what may be considered 
one of the greatest health problems of the age. From the standpoint 
of preventive medicine, it is proper to regard an outbreak of typhoid 
fever as a reproach to the sanitation and civilization of the community 


in which it was contracted. When the matter is better nnderstood health 
authorities will be held responsible for this and other preventable infec- 
tions, just as some one is now held responsible for preventable accidents. 

Much harm has been done by insisting that typhoid fever is in- 
fectious^ but not contagious; it is both — ^that is, communicable.^ 

Typhoid fever occurs both in endemic and epidemic forms. It 
may truly be regarded as pandemic. Xormally, typhoid fever is a 
warm weather disease. It recurs as an annual crop from July to Octo- 
ber.- Epidemics caused by infected water occur especially in the 
early spring, late fall, or winter months. Milk outbreaks may occur 
at any time of the year. Autumnal typhoid in our cities is due partly 
to infection contracted at health resorts, and has, therefore, been called 
a vacation disease. 

Typhoid fever is more prevalent in rural districts than in cities. 
In the United States there is more typhoid fever in the southern 
states than in the northern zone. The only explanation to account 
for this is the influence of temperature, rural conditions, and asso- 
ciation with the negro. Typhoid fever is no respecter of rich or poor; 
it attacks those in robust health, all ages, both sexes. 

Typhoid fever is a disease which ordinarily attacks the individual 
during the period of greatest economic value to the community. The 
economic loss, therefore, is appalling, and has been estimated to reach 
the sum of no less than $100,000,000 annually in the United States. 
Again, typhoid fever is an infection against which the individual* alone 
cannot protect himself wholly without the aid of the community. 

Prevalence. — Typhoid fever prevails more or less in all countries — 
the amount of the disease, however, varies greatly. It appears to be 
a disease of defective civilization, for those communities paying least 
attention to sanitation, as a rule, suffer most. In the United States 
there are comparatively few communities of 1,000 inhabitants or more 
which, during any period of twelve consecutive months within the last 
decade, have been entirely free from typhoid fever. According to the 
United States census report for 1900, the average typhoid death rate 
in the United States was 46.5 per 100,000 inhabitants. In 1908 the 
death toll from typhoid fever was no less than 35,000 in the United 
States. In other words, one person in about 200 in the United States 
contracted tv'phoid fever that year. It is estimated that in 1910-11 the 
number of deaths was reduced to about 25,000. The seriousness of 
these figures may be judged by estimating the probable number 
of cases of typhoid fever among persons handling the milk supply. 
Take, for instance, a city, as Washington, receiving its milk from a 

^ For distinction between these terms see page 317. 

^ In the southern hemisphere the typhoid season is during our winter. 



thousand dairy farms. On the average there will be about four per- 
sons on each farm who in one way or another come in contact with 
the milk. That makes 4,000 persons among whom about 200 cases of 
typhoid may be expected to occur annually. No wonder that milk- 
borne outbreaks of typhoid fever are common occurrences. 

The rate of prevalence of typhoid fever in the United States in 
comparison with the rates of many other countries is very high. Thus, 
the annual death rate from typhoid fever per 100,000 population for the 
period 1901-1905 was: in Scotland, 6.2; in Germany, 7.6; in England 
and Wales, 11.2; in Belgium, 16.8; in Austria (1901-1904), 19.9; in 
Hungary, 28.3 ; in Italy, 35.2 ; while the rate in the United States during 
the same period was about 46.5. 

A comparison between the prevalence of typhoid fever in this 
country and abroad is impressive. The following ten European cities 
with a total population of about 15,000,000 have an average typhoid 
rate of 2.4 per 100,000 during the 10 years 1901-10 1^ 




for 10 




for 5 



























1 4 


3 8 

4 1 

2 9 



3 3 

The following fifteen European cities with a population of about 
9,000,000 had a typhoid death rate of 5.3 per 100,000 in 1909 and 
only 4.5 in 1910 : 

'These facts and the following instructive tables are taken from: "The 
Necessity of a Safe Water Supply in the Control of Typhoid Fever," by Allan 
J. McLaughlin, U. S. Pub. Health lieports, XXVII, 12, March 22, 1912. 







, 2.6 




















The following eight European cities with a total population of 
7,500,000 had a typhoid death rate of 13.9 in 1909 and 15.6 in 1910. 
These rates would be considered low in America, but the European 
officials consider the persistence of such rates to be a reflection: 

















To recapitulate, in northern Europe the 33 principal cities, with 
an aggregate population of 31,500,000, had an average typhoid death 
rate per 100,000 population of 6.5 in 1909 and 1910. This includes 
such notorious typhoid centers as St. Petersburg, which had a rate of 
33.7 in 1910. The rate in St. Petersburg is considered to be due to 
the water supply, which is partly filtered and partly raw ISTeva water. 

Let us now compare these rates with typhoid fever in America: 




Birmingham, Ala. . . 
Los Angeles, Cal. . . . 

Oakland, Cal 

San Francisco, Cal. . 

Denver, Colo 

Bridgeport, Conn. . . 
New Haven, Conn. . 
Washington, D. C. . 

Atlanta, Ga 

Chicago, 111 

Indianapolis, Ind. . . 

Louisville, Ky 

New Orleans, La. . . 

Baltimore, Md 

Boston, Mass 

Cambridge, Mass. . . 
Fall River, Mass . . . 

Lowell, Mass 

Worcester, Mass.. . . 

Detroit, Mich 

Grand Rapids, Mich 
Minneapolis, Minn 

St. Paul, Minn 

Kansas City, Mo. . . 

St. Louis, Mo 

Omaha, Nebr 

Jersey City, N. J. . . 

Newark, N.J 

Paterson, N. J 

Albany, N. Y 

Buffalo, N. Y 

New York, N. Y . . . 

Rochester, N. Y 

Syracuse, N. Y 

Cincinnati, Ohio.. . . 
Cleveland, Ohio. . . . 
Columbus, Ohio. . . . 

Dayton, Ohio 

Toledo, Ohio 

Portland, Oreg 

Philadelphia, Pa 

Pittsburgh, Pa 

Scranton, Pa 

Providence, R. I.. . . 
Memphis, Tenn. . . . 
Nashville, Tenn .... 

Richmond, Va 

Seattle, Wash 

Spokane, Wash 

Milwaukee, Wis. . . . 

These 50 registration cities in the United States have an aggregate 
population of over 20,000,000. The average typhoid death rate in 
these cities for 1910 was 25 per 100,000 inhabitants. 



Unit of comparison 


Deaths per 
100,000 from 

fever, 1910 

33 principal European cities in Russia, Sweden, Norway, Austria- 
Hungary, Germany, Denmark, France, Belgium, Holland, Eng- 
land, Scotland, and Ireland 


6 5 

50 American cities of 100,000 inhabitants or over 


Excess of deaths from typhoid fever in American cities 


The excess of 18 deaths per 100,000 in the urban population alone 
shows that we have had, in the 50 cities mentioned above, at least 3,600 
deaMis, and probably 36,000 cases of typhoid fever, which were pre- 
ventable and should never have occurred. For the whole United States 
the number of cases for each year readily preventable by methods within 
our grasp would probably reach 175,000, and the deaths so avoided would 
total about 16,000. In 1909 there were more cases of typhoid fever 
in the United States than there were cases of plague in India, in 
spite of the fact that India's population is two and one-half times that 
of the United States. 





< 80 

H 60 


































Fig. 10. — Curve Showing Death Rate from Typhoid Fever in Albany before 


Eesidual or "Normal" Typhoid. — When a city such as Albany, 
Chicago, Lawrence, Lowell, or Pittsburg, which has been using grossly 
polluted water, is furnished with a water supply of good sanitary 
quality, there at once results a marked reduction in the amount of 
typhoid fever. The curve is not only lowered, but changed in char- 
acter (Fig. 10 — Albany). The remaining typhoid after the water- 


borne infection has been removed is known as residual typlioid, and 
the curve in such cases is spoken of as the "normal" typhoid curve. 
The normal curve shows a distinct summer prevalence recurring with 
marked regularity each year, and lacks the great irregularities which 
characterize the curve of a community drinking badly infected water. 
Normal typhoid is endemic typhoid; Sedgwick has proposed the name 
'"prosodemic" {proso, through, and demos, the people) as more ex- 
pressive of this type of the disease. The amount of residual typhoid 
varies markedly in different localities; thus it is twice as high in the 
southern as in the northern part of our countiy; it is much greater 
here than in most parts of Europe. 

Channels of Entrance and Exit. — The typhoid bacillus probably al- 
ways enters by the mouth. Typhoid fever is generally regarded as 
primarily a gastrointestinal infection, although the disease itself is 
not produced unless the blood, glands, and other structures of the 
body are invaded with the specific microorganism. The typhoid bacil- 
lus grows and multiplies in the intestinal tract, penetrates the mu- 
cosa, and thus invades the body. The bacillus leaves the body mainly 
in the feces and urine, occasionally in the sputum and other discharges. 
Typhoid bacilli appear in the feces early in the disease; sometimes be- 
fore the fever. Later in the disease they diminish in number and 
usually disappear during convalescence, although they may continue in- 
definitely (see "Bacillus Carriers," page 83). The feces may contain 
only a few typhoid bacilli ; usually they are present in consid- 
erable numbers; occasionally they occur almost in pure culture, prac- 
tically replacing the colon bacillus. 

Typhoid bacilli commonly appear in the urine about the second, 
third, or fourth week. They grow well in this fluid both within and 
without the body, and may be present in such enormous numbers that 
the urine resembles a 24-hour-old bouillon culture. From the stand- 
point of prevention, it is very important not to neglect the virus in 
the urine. Urotropin (hexamethylenamin) in ten-grain doses or more 
three times a day diminishes the frequency of typhoid bacilluria, and is 
also effective in curing this condition when once established. 

The sputum ordinarily, does not contain the bacilli unless there is 
a pneumonia or severe bronchitis. The bacilli may be eliminated with 
the discharges from abscesses, such as periostitis, months and even years 
after the disease. 

Diagnosis.' — An early diagnosis of typhoid fever is important not 
only for the successful treatment of the patient, but is of vital impor- 
tance in controlling the spread of the infection. The early diagnosis 
can only be assured tlirough laboratory methods. Typhoid bacilli 
may be isolated either from the blood or the feces. 

Blood Cultures. — Probably the easiest method, as well as the one 


giving the maximum information, is through blood cultures. The tak- 
ing of a little blood for this purpose is no more difficult or annoying 
to the patient than swaljbing the throat for diphtheria. A few drops 
of blood may be obtained by puncturing the lobe of the ear or the 
finger, with the usual precautions to prevent bacterial contamination. 
A much better method, however, consists in withdrawing 5 to 10 c. c. 
of blood by means of a syringe from one of the veins at the bend of 
the elbow. The technique is very simple, and, if the needle is sharp, 
the patient scarcely feels the puncture. In fact, if the attention of 
the patient is distracted a 'skillful operator can withdraw 10 c. c. of 
blood in this way before the patient is aware that anything has been 
done. The blood may be planted in bouillon, or, better, in bile. After 
24 hours in the incubator, any growth that occurs, is transplanted to 
other media, a pure culture obtained, and tested for agglutination. 
Usually a pure culture is obtained in the first medium, so that the diag- 
nosis may be established in 2-1 hours — at most, 2 or 3 days. 

Typhoid bacilli appear in the blood early in the disease, perhaps 
occasionally during the prodromal symptoms. Kayser obtained posi- 
tive results from 90 per cent, in the first week, 65 per cent, in the 
second, 42 per cent, in the third, 35 per cent, in the fourth. Our 
results in Washington were approximately the same. The typhoid 
bacilli probably do not gi'ow in the blood during life. Their presence 
in the blood stream represents an overflow from the spleen and lym- 
phatic tissues. The presence of typhoid bacilli in the blood may be 
taken to mean typhoid fever. The same cannot always be said if 
found in the feces or urine. 

The FECES.^From the feces or urine typhoid bacilli are best 
isolated upon Endo's medium. This consists of a 4 per cent, alkaline 
agar containing fuchsin, which has been decolorized with sodium sul- 
phite. Upon the surface of this medium typhoid colonies appear in 
24 hours as translucent, dewdrop-like colonies, whereas colon bacilli 
and other organisms that produce acid and split the fuchsin appear 
as red colonies. Suspicious colonies are fished and may be tested at 
once under the microscope for agglutination, or may be planted in 
bouillon to obtain a growth sufficient for macroscopic agglutination 
tests. In any critical case pure cultures should be obtained and studied 
for morphological, cultural, and other biological characters. A modi- 
fied Endo's medium and a rapid technique for diagnostic purposes, 
described by Kendall and used with success in my laboratory, are sum- 
marized as follows : 

Technique. — Make plain, nutrient, sugar-free agar as follows : Tap 
water (cold), one thousand cubic centimeters; powdered agar, fifteen 
grams; peptone (Witte), ten grams; meat extract (Liebig), three 
grams. Oook in double boiler one hour. Make the reaction just al- 


kuline to litimis by the cautious addition of NaOH. Cook fifteen 
minutes to set the reaction, and then liltcr throui^di absorbent cotton. 

Tlie tap water should be as cold as possible and the agar should be 
"dusted"" on the surface and allowed to settle into the medium before 
heat is applied and before the other ingredients are added. 

After filtrati(m, the medium is stored in flasks containing known 
amounts, conveniently in one hundred-cubic-centimeter lots, and steril- 
ized in the autoclave. 

To use the medium: (a) Prepare a ten per cent, solution of fuch- 
sin in ninety-six per cent, alcohol, (b) Prepare a ten per cent, solu- 
tion of sodium sulphite in water. 

Add one cubic centimeter of (a) to ten cubic centimeters of (b) 
and heat in the Arnold sterilizer for twenty minntes=(c). 

Add one per cent, of lactose (which must be chemically pure) to 
the agar medium described above, and heat in the Arnold sterilizer 
until the medium is melted and the lactose thoroughly distributed in 
it. The decolorized fuchsin solution (c) is then added in the pro- 
portion of one cubic centimeter of the mixture to each one hundred 
cubic centimeters of medium; then thoroughly mixed. 

Plates are then poured and allowed to harden (with the covers 
removed) in the incubator for thirty minutes, after which time they 
are ready for inoculation. 

Preparation of Feces for Inoculntion. — The feces are collected 
preferably in the small rectal tubes described by Kendall.^ A small 
portion of feces (about a loopful) is thoroughly emulsified in ten cubic 
centimeters of sugar-free broth, and preferably incubated one hour at 
37° C. prior to the inoculation of the ])lates. This preliminary in- 
cubation does two things : the clumps of bacteria settle down, leaving 
a more uniform suspension of bacteria in the supernatant fluid for 
inoculation, and the bacteria undergo a slight development in a medium 
particiilarly suited for their growth. The thin suspension of the stool 
is now rubbed upon the surface of the agar plates by means of a bent, 
sterile, glass rod, and the plates incubated for 18 hours at 37° C. The 
suspicious translucent, colorless colonies are removed entire to small 
test-tubes containing one cubic centimeter of broth and incubated for 
two hours at 37° C. At the end of this time there will bq sutlicient 
growth to make the customary microscopic agglutination tests. Con- 
firmatory cultural characters may be obtained by inoculating suitable 
media from the same tubes as those from which the organisms for 
agglutination were obtained. 

Physicians should encourage boards of health to furnish diagnostic 
aids of a laboratory nature. Such work should be in the hands of 
^Boston Med. and Surg. Jour., CLXIY, No. 1, Sept., 1911. 


specialists rather than entrusted to those who make occasional anal- 
yses. Early and accurate diagnosis is just as important to prevent the 
spread of other communicable diseases as it is with typhoid. These 
facts emphasized here will not be repeated under each disease. 

Bacillus Carriers. — In about 4 per cent, of all cases of typhoid 
fever the patient continues to shed typhoid bacilli in the urine or 
feces during and after convalescence. Some persons shed typhoid bacilli 
without a clinical history of having had the disease. We therefore 
recognize three kinds of carriers : acute^ chronic, and temporary. An 
acute typhoid bacillus carrier continues to discharge the infection not 
longer than 6 weeks follov/ing convalescence. A chronic carrier con- 
tinues to discharge the bacilli 6 weeks or longer. A temporary carrier 
is a person who has not had clinical typhoid fever but who discharges 
typhoid bacilli for a short period. Albert states that 25 per cent, of all 
chronic typhoid carriers have never had typhoid fever; and further 
estimates that one in every 1,000 of the general population is a carrier. 

While it would seem that typhoid bacilluria should be especially 
dangerous, a study of the cases indicates that most of the outbreaks 
that have been traced have been due to carriers who discharge the 
organisms in their feces rather than in the urine. It seems that 
typhoid carriers are more dangerous in certain seasons. More cases 
are traced to women ^ than to men. This is probably owing to the 
fact that the chief danger lies in handling foodstuffs, so that a carrier 
occupied as a cook or waitress is a special menace. 

The question of preventing the spread of the disease through bacil- 
lus carriers is important and difficult. Surgical methods fail to cure 
carriers, for the typhoid bacillus may continue to grow in other parts 
of the intestinal tract than the gall bladder. Medical measures, such as 
urotropin, are efficient for bacilluria, but are of no avail in the fecal 
carriers. Attempts have been made to relieve the condition by the use 
of bacterial vaccines. Petruschky - and also Meader have reported en- 
couraging results, especially with the use of autogenous cultures. So 
far certain cases resist all attempts to relieve the condition. It is unnec- 
essary to place bacillus carriers incommunicado. It is sufficient to re- 
strict their activities so that they may neither infect food nor their sur- 
roundings. With proper care and cleanliness typhoid carriers may pre- 
sent little danger to their fellow men. The problem, at present, is to 
detect the carriers, so as to establish a sanitary isolation, if not an 
actual quarantine.^ 

Resistance of the Virus.- — The typhoid bacillus has no spore. It is, 

therefore, comparatively easy to destroy. The only difficulty present- 

^ Women are more subject to gall-stones. 
""Deut. med. Wochschr., July 11, 1912, XXXVIII, 28. 

^ The facts covering the infectivity of carriers are summed up by Ledingham, 
39th An. Eeport Local Gov. Board, 1909-10, Supplement, p. 249. 


ing itself is getting at the bacillus Avlien imbedded in fecal masses. 
Wlien dry, most typhoid bacilli die in a few hours; occasionally a 
few survive for months. The fact that typhoid bacilli are killed by 
drying renders infection through dust unlikely. 

When a moist medium, such as water, milk, or urine, is lieated to 
60° C, practically all the typhoid bacilli such a medium may contain 
are killed. An exposure at (50° C. for 20 minutes will surely kill all 
of these microorganisms. They are not destroyed by freezing (see 
"Relation to Ice," pages 837 et seq. 

Jn their resistance to germicides tyi)hoid bacilli behave like the 
average non-spore-bearing bacilli. Thus bichlorid of mercury, 1- 
1,000, phenol, 2i/2 per cent., formaldehyde, 10 per cent., are effective 
upon the naked germs. In order to kill the typhoid bacilli in feces 
special precautions or stronger solutions are necessary (see page 1030). 

The viability of typhoid bacilli in feces is very variable, depending 
on the composition of the feces and the varieties of other bacteria 
present. Sometimes the typhoid bacilli in feces perish in a few hours, 
usually in a day; under exceptional circumstances they may live for 
much longer periods. In the Plymouth epidemic typhoid bacilli prob- 
ably remained alive and virulent in the feces, exposed to the winter's 
cold, for several months. Levy and Kayser found they remained alive 
in feces for 5 months in the winter. The life of the organism in 
privies and in water is usually comparatively short. In nature they 
die, as a rule, in water in about 7 days and often after 48 hours. They 
probably live longer in clean water than in contaminated water. In 
the outer world symbiosis plays an important part, also the presence 
of deleterious chemicals, temperature, light, desiccation, dryness, and 
other factors known to be injurious to spore-free bacteria. As a rule, 
the typhoid bacillus does not survive long in the soil under the usual 

Typhoid Bacillus in Nature.' — The typhoid bacillus should be re- 
garded as a pathogen, not as a saprophyte. It lives and grows prin- 
cipally in the human body. It has a tendency to die in water, air, 
soil, upon fomites, or in nature generally. The grand exception to 
this statement is in the case of milk, in which the typhoid bacillus 
grows well. 

The typhoid bacillus is much more widely distributed in man than 
the cases indicate. Thus, in the District of Columbia, of 1,000 healthy 
persons examined during the typhoid season of 1908, typhoid bacillus 
was found in the feces in 3 instances. At least one and perhaps two of 
these individuals were regarded as temporary carriers. In each instance 
the organisms were found only once. The population of the District of 
Columbia in 1908 was 300,000, and at the ratio of 1 per 1,000 this 
would represent about 300 healthy persons in that community har- 

TYPHOID FEVER: 1902 TO 1906 
Death Rate per 100,000 of Population 

'Richmon6 borough.K.y. 


San Anfonio. Taos 

Meu) Orleans, Ua. 
Covington. Ky. 


Memphis , T£nn 


Springfield, 111. 
Harrisburg. Pa. 

Cincinnati, Ohio 




Fall River,<Hass. 






MilwauKec U)is. 
Chicago, II I. 
Buffalo, «.«. 
Erie, Pa. 





Worcester, Mass. 




Boston, aass. 

Chelsea Mass. 


lOaterbur y Conn. 

Scranf on. Pa. 

Bronx borougd. (ST. y. 
ilanliaUan forough.JT.y, 

BaUimon- MA 

Broohlyn toxoush.X.M. 


Fig. 11. — Influence of Public Water Supplies on the Typhoid Fever Death Rate. 
(Diagram prepared by Marshall O. Leighton, U. S. Geological Survey, from figures 
furnished by Dr. Cressy L. Wilbur, Chief Statistician of Vital Statistics, Bureau 
of the Census — from Kober.) 

8 85 


boring and shedding typhoid bacilli for a brief period of time during 
the typhoid season. 

Modes of Spread. — Typhoid fever is spread either by direct or in- 
direct contact — indirectly through water, milk, and other foods; through 
"contacts," and also flies, fingers, and fomites. Each of these modes 
of spread needs separate consideration. 

Water. — Water-borne typhoid is a common occurrence. Xot long 
ago it was regarded as the sole or usual mode of spread; now we know 
that this was a mistake. Most fecal matter ultimately finds its way 
to water; most water courses draining inhabited regions are contam- 
inated with human feces. Surface water is, therefore, apt to contain 
typhoid bacilli. The fact that there may be no clinical case of typhoid 
fever in the drainage area is no guarantee that the water may not be 
infected — in view of the prevalence of missed cases and bacillus car- 

Fortunate]}'', typhoid bacilli do not grow and multiply in water 
under natural conditions. They usually die in a few days, and rarely 
persist longer than T days. They succumb more quickly in some waters 
than others, more quickly in summer than winter. Thus Reudiger ^ 
has shown that typhoid bacilli die less quickly in the Red Lake River 
in ^Minnesota when exposed in dialyzing membranes in the river with 
ice than in the open river. He also showed that colon bacilli as well 
as typhoid bacilli disappear much more rapidly from polluted water 
during the summer months than during the winter months when the 
river is protected with a covering of ice and snow. Reudiger considers 
that the destruction of the typhoid bacillus in river water during 
the summer months is in a large measure due to the growth of micro- 
scopic plants, and other organisms which give off dialyzable substances 
which are harmful to B. tj/phosiis. One of the reasons for believing 
in the existence of such poisons in water is the fact that typhoid cul- 
tures in a collodion sac placed in water die more quickly than other- 
wise. Further, the effect of the direct rays of the sun are entirely 
lost when the river is covered with ice and snow. 

Water plays a large but diminishing role in the spread of the 
typhoid bacillus. The great water-borne epidemics have overshad- 
owed the other media of communication. We know that the larger 
part of the typhoid now prevalent in tliis country is not water-borne; 
Whipple in 1908 estimated it at 35 per cent. ; it is now no doubt much 
less. Typhoid fever may be excessively prevalent, even epidemic, in 
a city having a water supply of good sanitary quality. 

In the vast majority of cases water-borne typhoid is contracted 
from a surface supply, that is, a river, small stream, pond, or lake. 

Wour. Am. Puh. Health Ass., June, 1911, Vol. I, No. 16, p. 411. 



Ground water becomes a source of clanger onh' under special condi- 
tions (see chapter on water). 

Water-borne epidemics present certain definite characteristics. They 
almost always occur in the spring, fall, or winter, when the water 
is cold. Most of the great water-borne epidemics have occurred in 
northern cities, both in this country and in Europe. They usually 
have a sharp onset, the curve rises to a peak, and declines rapidly. 
The pollution is usually nearby; that is, there is a rather direct trans- 
fer of fresh virulent infection. Granting that the typhoid bacillus 
does not grow in cold water, there must be a very considerable dilution 
in most of the epidemics. 


JBURGH, Pfl. - 

-Typhoid Fe 


D£/ITH RATE PER 100.000 /900 TO 1910 


















L i 























i^ 1 









§ 1 

b- 1 

























FiQ. 12. 

-Immediate and Striking Effect of Purifying a Badly Infected Water 
Supply upon the Typhoid Situation. 

The following examples are given of the fact that water-borne out- 
breaks of typhoid fever occur during the winter, fall, or early spring, 
when the water is cold. Thus we have the water-borne epidemic in 
Plymouth, Penn., in 1885, which began with the spring thaw and 
was doubtless produced from the frozen accumulation of typhoid ex- 


crement from a single case. Very similar to the Plymouth outbreak 
was that at Xew Haven, Conn., in 1901. The outbreak at Ithaca, 
X. Y., started in epidemic proportions in January, The epidemic 
in Shorbourno, England, in 1873, likewise started in January. Four 
acute epidemic exacerbations are recorded in Philadelphia in Decem- 
ber of the years 1884, 1890, 1899, and 1903. Several similar epi- 
demics have occurred in the winter time in Chicago — one in January, 
1890, another in January, 189(5, and one in March, 1891. Another 
striking instance is the epidemic in Xewark. X. J., in February, 1899, 
and one in December, 1891. Abroad, epidemics are recorded in Ber- 
lin in February, 1899, in Paris in February, 1894, and in Vienna in 
Xovember, 1888. All of these are generally believed to have been 
water-borne and must have taken place when the water was very 
cold. In fact, as previously pointed out, extensive water-borne epidemics 
of typhoid fever rarely occur in the summer time. 

The epidemiology of water-borne typhoid caused by distant, 
diluted and attenuated infection is not understood. It was formerly 
thought that a high typhoid rate necessarily meant badly infected 
water. We know now that this does not necessarily follow, as has been 
proven by the experiences in Washington, Winnipeg, army camps, and 
many southern cities. 

Almost all the water-borne epidemics of typhoid fever rest upon 
circumstantial evidence. It is difficult to isolate the typhoid bacillus 
from water, and the damage is usually done before suspicion points to 
the water.^ 

It is clear that in cities which have had safe water supplies for a 
period of years the rate should not be above 5 per 100,000, unless some 
unusual condition exists, such as poor control of milk or lack of con- 
trol over patients and carriers, and disregard of modern sanitary knowl- 

Xo single measure in reducing typhoid fever on a large scale ap- 
proaches the effect of substituting a safe for a polluted water supply. 
As an instance of this wholesale saving of human life, tlie reduction of 
typhoid fever in four American cities is shown in Fig. 13, p. 89. 

Ice. — Ice may, under exceptional circumstances, occasionally be the 
vehicle by which typhoid bacilli are transferred. Freezing does not 
kill B. typhosus, but there is a great quantitative reduction not only 
in the act of freezing, but during storage, hence the danger is greatly 
lessened. The most suggestive outbreak of typhoid fever attributed to 
ice was reported by Hutchins and Wlieeler in 1903 in the St. Law- 
rence Hospital, three miles below Ogdensburg. A few other instances 
in which ice is believed to have conveyed the infection have been re- 

* Examples of Trater-borne outbreaks of typhoid fever will be found in the 
chapter on water. 



ported, but are based upon flimsy evidence. The fact that natural 
ice is usually stored many weeks or months before it is used is a sani- 
tary safeguard. Manufactured ice made from distilled water and 
handled with cleanly methods is above reproach. For a discussion of 
ice in relation to typhoid fever and other infections see page 840. 

Q SO 4.0 6 80 lOO 120 140 |60 ISO 200 | 

1003 IH 

1904 ^B 



WakftrTowa, >CY1 















1338 H 

1899 p 




^^M \ 



^— I^^M 



^g— p. j—p 

CtncinnaVu Ohio. 

Fig. 13. — ^Abeupt Reduction in Death Rates from Typhoid Feveh Incident to 
Water Purification in Four American Cities. 

Milk. — Trask collected 317 typhoid epidemics up to 1908 caused 
by infected milk. Since then many more instances have come to light. 
Doubtless many milk outbreaks have escaped attention or have been 
attributed to water or other sources. The typhoid bacillus grows well 
in milk, and it is now realized that this medium is a frequent and 
important mode of communication. Most milk outbreaks are reported 
either in England or America. On account of the almost universal 
custom of boiling the milk in European and tropical countries, milk 
outbreaks are rarely reported from these regions. During the four years' 
study of typhoid fever in Washington, it was found that at least 10 
per cent, of the cases were milk-borne. 

The milk usually becomes contaminated on the farm, from a case 
or a carrier. It may also become infected in transportation, at the 
city dairy, or in the home. Milk outbreaks come abruptly, rise to a. 
peak like a water epidemic, and subside rather sharply. There are 
comparatively few secondary cases. Milk-borne epidemics of typhoid 
fever have certain characteristics which permit ready recognition. 

(a) There is a special incidence of the disease on the track of the 
implicated milk supply. The outbreak is localized to such areas. 

(b) The better class of houses are invaded, and persons in better cir- 
cumstances generally suffer most. 


(c) Those who drink milk are chiefly affected and those suffer 
most who are hirge consumers of raw milk. 

(d) The incidence is high among women and children. 

(e) The incubation period is shortened perhaps on account of the 
large amount of infection taken. 

(f) More than one case occurs simultaneously in a house. This 
is a very suspicious circumstance to the epidemiologists. The first in- 
dication of a milk outbreak in a city with a good water supply is 
usually the fact that two or more persons in a household came down 
with typhoid fever within a few days of each other. 

(g) Clinically the disease usually runs a mild course, owing to the 
fact, no doubt, that the virus becomes attenuated in the process of multi- 
plication in the milk. In water-borne typhoid the same germs are in- 
gested that were passed; in milk-borne typhoid it is the succeeding gen- 
erations that are ingested. 

Milk-borne outbreaks are sometimes very extensive. One of the 
largest epidemics occurred in Boston (Jamaica Plain) in March and 
April, 1908. Four- hundred and ten cases were reported; 348 of them 
drank the suspected milk. Among the first victims of the disease was 
the milkman, who was believed to have infected the milk through 
tasting it. The number of persons involved in a milk-borne epidemic 
varies greatly, depending upon the amount of milk infected and other 
factors. It must not be uncommon for a single bottle of milk or a 
small quantity to become infected, and thus transmit the disease to one 
or two persons. Such instances are exceedingly difficult to trace. Oft- 
times the milk becomes infected from a carrier. An instance of this 
occurred in Washington (Georgetown) in 1908. In this case the milk- 
maid had typhoid fever 18 years previously. Examinations showed 
almost pure culture of B. typhosus in her feces. Fifty-five persons 
who drank the infected milk contracted the disease. 

Milk Products. — Fresh milk products, such as cream, ice-cream, 
butter, and buttermilk, and fresh cheese, may contain the typhoid 
bacillus, and are occasionally media of communication. 

Cream contains more bacteria than the milk from which it is taken. 
The use of infected cream in coffee, on cereals, etc., is sufficient to 
cause the disease. Several instances in the Washington studies were 
traced to such use of cream. As a rule, coffee in the cup is not hot 
enough to kill the typhoid bacillus. 

Freezing kills only a certain percentage of the typhoid bacilli. In 
Washington several cases of the disease were traced to ice-cream. 

Bruck has shown that the typhoid bacillus will live in butter for 
27 days. 

Buttermilk may be quite as dangerous as the cream from which it 
is derived. In cheese the time of fermentation, symbiosis, etc., les- 


sens the likelihood of survival of the typhoid bacillus. Fresh cream- 
cheese, such as Cottage cheese, may be responsible for an occasional 

Oysters, Mussels, and Shellfish. — The first outbreak of typhoid 
fever attributed to this source was investigated by Conn at Wesleyan 
University, Middletown, October, 1894. Twenty-five cases were at- 
tributed to eating infected oysters; 4 died. Not all of those who took 
sick had clinical typhoid fever. Some had gastrointestinal disturbances 
with illness lasting but a few days. About one-quarter of those at- 
tending the dinners at which the oysters were served were made ill. 

A similar instance occurred at the Mayors' banquets at South 
Hampton and Winchester, in 1903. 

In the Washington studies it seems that oysters and shellfish play 
a minor role in the spread of the disease, which occurs mostly in 
the summer time, while oysters and similar sea food are relished mainly 
in winter. Comparatively few of the cases studied gave a history of 
having eaten oysters within 30 days prior to the onset of the disease. 
Oysters become especially dangerous when consumed soon after tak- 
ing them from a polluted bed, or when floated or bloated in infected 
water. (For further discussion of this topic, see page 566.) 

Fruits and Vegetables. — Vegetables, such as celery, lettuce, and 
radishes, partaken of raw, and grown on land fertilized with fresh night 
soil, may be dangerous, and this probably accounts for an occasional 
case. In large cities it is practically impossible to trace this source 
of infection. It therefore remains more a suspicion than a conviction. 
In Hackney, London, two local outbreaks were traced to watercress 
taken from a polluted stream. In Springfield, Mass., an outbreak 
which occurred in the summer of 1905 was attributed to infected fruits 
and vegetables. 

Creel ^ found typhoid bacillus upon the tips of leaves of plants 
cultivated in contaminated soil. Under conditions most unfavorable to 
the B. typhosus the infection lasted at least 31 days — a period suffi- 
ciently long for some varieties of lettuce and radishes to mature. 

Flies. — The evidence is now complete that the common house fly 
(Musca domestica) may convey the infection of typhoid. It is not 
inappropriately called the typhoid fly. The typhoid bacilli may be 
smeared upon the feet or other parts of the insect, or may live in the 
intestinal tract and pass in the dejecta in almost pure culture. Flies 
live, feed, and breed in fecal matter and decomposing organic substances 
of all kinds. It is easy to see how they may convey infections from 
this source to our food, lips, or fingers. Alice Hamilton isolated typhoid 
bacilli from 5 out of 18 house flies captured in Chicago in the privy 
and on a fence near a sick room. It has been shown experimentally that 

"-PuUic Health Reports, Feb. 9, 1912, p. 187, XXVII, 6. 


living typhoid bacilli may remain upon the bodies of flies for as long 
as 23 days. Special attention to the role played by the fly was given 
by Reed, Vaughan, and Shakespeare in their studies of the prevalence 
of typhoid fever in our army camps in 1898. They concluded that 
flies undoubtedly served as carriers of the infection and attributed 
about 15 per cent, of the cases to this mode of communication. They 
found that "flies swarm over infected fecal matter in the pits and then 
deposit it and feed upon the food prepared for the soldiers at the mess 
tents. In some instances, where lime had recently been sprinkled over 
the contents of the pits, flies with their feet whitened with lime were 
seen walking over the food." The danger from fly transmission varies 
very much, and depends upon circumstances. In a camp it is con- 
siderable; in a well sewered city the risk is diminished. In our Wasii- 
ington studies we could find no relation between fly abundance in the 
simimer of 1908 and typhoid prevalence. It is not possible to express 
mathematically the percentage of cases caused by flies — the figures would 
vary greatly, depending upon circumstances. The danger of typhoid 
from flies in cities has doubtless been overstated. However, if only 
one per cent, of the cases were thus transmitted, the suppression of 
flies would still be quite worth while (page 223). 

Dust. — Typhoid bacilli soon die when dried, especially when ex- 
posed to the sun and air. Dust-borne infection in this disease must 
be rare. In the South African war there were frequent dust storms 
in some localities, so that the food was covered with dust and sand. 
Some of the infection was believed to have been conveyed in this way. 

FoMiTES. — The infection may be conveyed upon soiled linen, blan- 
kets, and other objects. It was believed by Reed, Vaughan, and Shake- 
speare that the clothing, blankets, and tents in the Spanish-American 
war became infected and were a prime factor in spreading the dis- 
ease. After the South African war some of the blankets used by the 
troops were sent back to England and used on a training ship, on 
which typhoid fever appeared. The blankets were found to be dirty 
and soiled with fecal matter, from which Klein is reported to have 
obtained living typhoid bacilli. The danger of fomites contaminated 
with fresh infection is real, and emphasizes the importance of dis- 
infecting bedding, towels, and other fabrics. 

Soil. — The soil, long regarded as the most important factor in the 
spread of typhoid fever, and by Pettenkofer and others considered an 
essential element, is now given scant consideration. Pollution of the 
soil, however, cannot be disregarded. The typhoid bacillus may live 
for a long time in sewage-soaked earth. A surcharged soil may en- 
danger the water, milk, and other foods, or infect through flies and 
other means (see Soil). 

Contact Infection. — "Contact" is a convenient term to indicate 


the spread of infection directly or indirectly as a result of close asso- 
ciation between the sick and the sound. Actual contact is not neces- 
sarily implied. The term is used to indicate the transfer of the in- 
fection through a short intervening space in a brief period of time 
(see page 31i). Thus the infection may be passed from one to an- 
other through kissing, soiled hands, remnants of food, infected ther- 
mometers, or tongue depressors, contaminated towels or other fabrics, 
cups, spoons, glasses, etc. If the nurse infects a cup of milk or glass 
of water that carries the infection to another member of the house- 
hold, such cases are included under ''contacts." The infection may also 
be spread in the household hj flies, fingers, and various other means, 
usually difficult to trace, and which are, therefore, all included under this 
group. Eegarded in this light, contacts play a major role in the spread 
of the disease. 

Extensive municipal outbreaks have been reported as largely or en- 
tirely due to contact infection. Winslow in 1901 studied such an out- 
break in Newport. Others have been reported from Knoxville, Winni- 
peg, Springfield, and from Germany and England. Koch regarded 
the spread of typhoid in Trier in the light of contact infection. Free- 
man says that the majority of outbreaks in the smaller towns of Vir- 
ginia are due to this cause. Extensive outbreaks in institutions are 
often due to contact with mild cases or carriers. Flies, fingers, and 
food (Sedgwick), and dirt, diarrhea, and dinner (Chapin), which too 
often get sadly confused, explain the occurrence of many a case of con- 
tact infection in typhoid fever and other infections. 

In army camps with clean water and good milk, contact infection 
may rise to epidemic proportions. In the Spanish-American war, of 
107,000 of our troops in camp, 20,000 contracted typhoid, mostly by 
"contact/* Similar conditions prevail in rapidly growing cities, in 
crowded apartments, and congested regions with a susceptible population 
and other favoring conditions. The danger of contact is well shown 
by the frequency with which nurses, ward attendants, house physi- 
cians, and others similarly exposed take typhoid fever. Studies of the 
incidence of the disease in the Massachusetts General Hospital, Bos- 
ton, in the Presbyterian Hospital, Philadelphia, and the Johns Hop- 
kins Hospital, Baltimore, show that typhoid fever is at least twice and 
may be 8 times as prevalent among those who come in close and fre- 
quent association with the patient as among the population at large. 
Further, the disease contracted under such conditions seems to run a 
course of more than ordinary severity, with a greater number of com- 
plications and with a high mortality. This is doubtless due largely to 
the fact that the contactors receive fresh virulent virus. 

In our studies of typhoid fever in Washington we were impressed 
with the importance and frequency of contact infection in that en- 


demic center. In 1907 we attributed 6 per cent, of the cases to con- 
tacts; in 1908, 15 per cent., and in 1909, 17 per cent. This included 
only contact with cases during the febrile stage of the disease. In 
Strassburg. Kayser attributed 1G.8 per cent, of the cases occurring 
during 3 years in that city to contact infection. Little groups of 4, 
6, to 12 or more cases following a primary case in a suburban focus, 
in my experience, frequently fall in the category of contacts. 

According to Conradi, the infection is transmissible most often 
during the early stages of the disease, sometimes even during the 
period of incubation. The Washington studies do not support this 
view, for we found the disease is communicated during all stages, and 
especially during convalescence. This may be due to the fact that 
during this time the patient moves about and scatters the infection 
over a wider radius. 

Typhoid fever, in view of all the facts, must now be regarded as a 
"contagious" disease. We will never have an end of it until it is so 
regarded and treated accordingly. 

Preventive Typhoid Inoculations.- — An active immunity to typlioid 
fever may be artificially induced by introducing dead typhoid bacilli 
into the subcutaneous tissue. Living cultures or bacillary extracts 
may also be used. The procedure is harmless, rational, and effective. 

Our knowledge of inoculations against typhoid fever began with 
the work of Pfeiffer and Kolle,^ who inoculated two volunteers in 

1896. About the same time Almroth Wright ^ inoculated several per- 
sons, and in 1898 continued the work upon an extensive scale in India 
upon 4,000 British soldiers. In 1900, during the Boer war. Wright, 
together with Leishman, prepared a vaccine ^ and supervised the inocu- 
lation of 100,000 British troops. The results in India were quite en- 
couraging, but for various reasons the same procedure in South Africa 
was not as satisfactory as had been anticipated. Prophylactic inocula- 
tion on the advice of Koch was used by the Germans in the Herero 
campaign in southern West Africa in 1904. The prophylactic was 
voluntary and only about half of the command (7,287 men) availed 
themselves of it. The results, while good, fell short of expectations. 
In this country Richardson was the first to advocate and practice 
inoculations as a means of protection against typhoid fever. The best 
results have been obtained in the United States Army under the direc- 
tion of Major Russell. 

Leishman* in his Harben lecture (1910) explains the lack of suc- 

•Pfeiflfer and Kolle: Deutsche med. Wochnschr., 1896, XXII, 735. 

= Wright: Lancet, London, Sept. 19, 1896, 807; Brit. Med. Jour., Jan. ,30, 

1897, 16. 

^ The material injected is called a vaccine and the process spoken of as vacci- 
nation. The term in this connection is a little confusing. Inoculation is better. 
* Leishman, W. B.: Jour. Eoy. Inst. Pub. Health, London, 1910, XVIII, 394. 


cess in early years by saying tliat the vaccine may have been made less 
efficient by the use of too great heat in killing the bacilli. Further, it 
should be noted that smaller doses and fewer injections were given then 
than now. 

The typhoid vaccines may be prepared in a number of different 
ways. Usually dead bacilli are used, although live bacilli have been 
inoculated. The bacilli may be killed either with the aid of heat or 
germicidal substances; the dead or live bacilli may be sensitized by the 
addition of antityphoid serum ; the vaccines may be prepared with pul- 
verized bacilli, from bacillary extracts, or by the use of various chem- 
ical methods. 

Usually the vaccine is made from a twenty-four-hour-old culture 
killed by heating to 60° C. for one hour or less. Overheating prob- 
ably impairs the immunizing power of the vaccine. Most typhoid 
bacilli die before the temperature reaches 60° C. Some of the strains 
have a lower thermal death point. Stone heats only to 53° C. for one 
hour, depending upon phenol (0.5 per cent.) to sterilize the culture. 
Cultures killed without heat have perhaps greater protective properties. 

Certain cultures seem to cause the production of more antibodies 
than others. In the earlier work it was believed that the more viru- 
lent strains produce a greater protection. This is doubtful, for it ap- 
pears that the protection afforded is not in proportion to the local or 
general reaction, but to the amount and variety of antibodies stim- 

The injections are given subcutaneously at intervals of five days. 
From 50,000,000 to 100,000,000, sometimes 1,000,000,000, dead typhoid 
bacilli are injected at each inoculation. The number of inoculations 
varies with different authorities. At least 3, preferably 4, should be 
given; the greater the number of injections the greater the immunity 

A reaction at the site of the inoculation occurs in about 10 per 
cent, of persons. The reactions are ■ usually moderate and never se- 
rious. They consist of local manifestations, of irritation, and inflam- 
mation about the site of inoculation, such as pain, redness, swelling, 
edema; also general symptoms, such as malaise, pains in the back and 
limbs, and fever. Children, as a rule, react less than adults. Of 1,101 
persons inoculated by Hartsock, 11 per cent, showed no reaction, 83 
per cent, mild reaction, 5 per cent, a moderate reaction, and 1 
per cent, a severe reaction. All the cases had a slight local tenderness 
and redness at the point of inoculation. The symptoms of the reac- 
tion usually pass in 24 hours. The number and character of the re- 
actions in the experience of the United States Army ^ are shown in the 
following table: 

^Eussell, F. P.: Jour. A. M. A., LVIII, No. 18, May 4, 1912. 



Number of 











Third dose 


The best time to give the treatment is late in the afternoon, for 
then tlie severest part of the reaction is over by the morning. The 
injections are usually given into the subcutaneous tissue of the outer 
side of the arm or into the abdominal wall; sometimes the interscapular 

There is no laboratory inde.x of the degree or duration of the im- 
munity produced as a result of the inoculations. The following anti- 
bodies appear in the blood: agglutinins, precipitins, opsonins, lysins, 
stimulins. There are factors involved in the immunity not understood, 
and, therefore, the presence or absence of typhoid fever among in- 
dividuals protected in this manner is the only index of value. 

The negative phase advanced by Wright and denied by Leishman 
and others probably does not occur. At least there appears to be no 
increased susceptibility to the disease during the so-called negative 
phase. There is, therefore, no known objection to giving the prophy- 
lactic to those exposed to the disease or during an epidemic. In fact, 
the vaccines have been used as a therapeutic agent during the illness. 

The immunity varies in degree and also in duration; at least one 
year (Pfeiffer and Kolle's vaccine) ; four years (Wright's vaccine). 
On the average, the immunity may probably be depended upon for 2 or 
3 years when produced by 4 injections of dead bacilli. The immunity 
may be prolonged or renewed by recourse to reinoculation. One attack 
of typhoid fever, however mild, produces, as a rule, a lasting immunity. 
Second attacks, however, occur. Draschfeld's figures, based on 2,000 
persons in the Antwerp Hospital, show that only 0.7 per cent, of that 
number were affected twice. 

The results of typhoid inoculations can no longer be questioned. 
The morbidity is lowered in those who have been properly "vaccinated"; 
the figures are too recent to state just how much. The most striking 
effect is in the lowering of the mortality. The latest summing up 
of the antityphoid inoculations is by Leishman in the July and Sep- 
tember, 1910, numbers of the Journal of the Royal Institute of Public 
Health, xviii, Nos. 7, 8, and 9; also Report of the French Commis- 
sion, Public Health Reports, P. H. & M. H. S., October 6, 1911, xxvi, 
40, 1507. 

The best results have been obtained in the United States Army, 


where the vaccinations are done under the supervision of Major Rus- 

The health record established by the Maneuver Division of the 
United States Army at San Antonio, Texas, during the summer of 
1911, is a triumph in preventive medicine. The division had a mean 
strength of 12,801 men. All were treated with the typhoid vaccines. 
The result was that from ]lilarch 10th to July 10th only two cases 
of typhoid fever developed; no deaths. One patient was a private 
of the hospital corps w'ho had not completed his immunization, having 
taken only two doses. His case was very mild and probably would 
have been overlooked but for the rule that blood cultures were made 
in all cases of fever of over 18 hours' duration. The other case was 
a teamster who had not been inoculated. Among the 12,801 men 
there were only 11 deaths from all diseases. Typhoid fever prevailed 
at the time in the neighborhood. Thus, there were 19 cases of tj^phoid 
fever with 19 deaths in the city of San Antonio during this period. 
This contrasts markedly with the typhoid record of the United States 
Army during the Spanish-American war, when the typhoid record 
of a division of volunteer troops camped at Jacksonville, Florida, in 
1898, under conditions similar to those at San Antonio, was as fol- 
lows : The division at Jacksonville had 2,693 cases with 218 deaths, 
which was about the average typhoid incidence of the camps. Since the 
year 1904, with an improved vaccine, more than 100,000 British troops 
have been inoculated without any untoward result. The protection 
afforded may be seen from the most recent figures from India, re- 
ported by Col. R. H. Firth.2 

"In that period there were, in all India, 112 cases of typhoid, with 
six deaths, among the protected men, and forty-five cases with four 
deaths among the non-protected. The protected population was 63,624 
persons, and the non-protected 8,481. From these data we find the 
case incidence per thousand among the protected to be 1.7 and among 
the non-protected to be 5.3. If we take the mortality and express it 
as per million, then the ratio for the protected is 94, and for the non- 
protected 471. That is to say. the incidence for typhoid for the first 
half year was roughly five times as great among the non-protected as 
among the protected." 

Spooner reports that in the Massachusetts General Hospital, among 

the nurses and others exposed to typhoid fever, 80 per cent, of whom 

have been inoculated during the past three years, not a case has been 

contracted, and for the first year in the history of the institution there 

were no cases among the nurses or attendants. The case morbidity in 

training schools for nurses in Massachusetts during three years was 

nearly nine times greater in the uninoculated than among the inoculated. 

^ Loc. cit., p. 95. 

-Firth, E. H. : Jour. Boy. Army Med. Corps, London, 1911, XVII, 495. 


Melchnikolf and Besredka * failed to protect chimpanzees against 
typhoid infection by means of killed bacilli, but obtained immunity ap- 
parently as definite as tiiat produced by an attack of the disease by the 
use of living cultures. - 

Summary. — Pi'evcntive typhoid inoculations involve no risk what- 
ever, and are especially applicable to those unduly exposed to the in- 
fection, such as nurses, hospital attendants, physicians, travelers, sol- 
diers in camps, persons in epidemic localities, and persons in the fam- 
ily of a bacillus carrier. The method has been proposed for general 
use among the public in endemic foci, but it is a question whether this 
artificial method of acquiring immunity would serve as good a purpose 
in the end as fighting the disease along the lines of general sanitation 
— which has been so successfully done in many European centers. It 
would certainly be a mistake to immunize the population with this 
artificial method to the neglect of general sanitary improvements, such 
as good water, clean milk, fly suppression, cleanliness, and personal 
hygiene. The question as to whether the vaccinations may or may 
not increase the number of bacillus carriers should also be determined. 
Because a person has received the protection aflforded by typhoid inocu- 
lations is no reason for reckless disregard of other prophylactic meas- 

Management of a Case so as to Prevent Spread.— Success depends 
upon an early and accurate diagnosis. All cases of typhoid fever and 
all cases suspected of being typhoid fever should be isolated. This 
does not mean imprisonment in a lazaretto. The proper place to care 
for typhoid fever is in a suitable hospital. A private home is a poor 
makeshift for a hospital, and it is unreasonable to turn a household 
into a hospital for 4 to 8 weeks or longer. The room in which the 
patient is treated should be large and well ventilated, and should con- 
tain no unnecessary furniture, curtains, carpets, etc. It must be kept 
scrupulously clean, dry sweeping and dusting prohibited; and well 

The case should be reported to the health authorities without de- 
lay, and the house should be placarded so as to warn others, and visit- 
ing discouraged. Under no circumstances should visitors be admitted 
into the sick room. 

The disinfection of the stools, urine, sputum, and other excretions 
is of the first importance, and should be carried out with great care 
and conscientiousness. For the urine, sufficient bichlorid may be added 
to make a 1-1,000 solution, or carbolic, 2.5 per cent., formalin, 10 per 
cent., and allowed to stand one hour before discarding. Stools may 
be disinfected with bleaching powder, 3 per cent.; milk of lime (1 to 8) ; 

^Annales de I'lnst. Pasteur, Dec, 1911, XXV, 12, p. 865. 
''Ann. de I'lnst. Pasteur, Mar. 25, 1911, and Dec, 1911. 


cresol, 1 per cent.; carbolic acid, 5 per cent.; or formalin, 10 per cent. 
The discharges should be received in a glass or earthenware vessel con- 
taining some of the germicidal solution. Then add more of the solution 
so that it shall be present in twice the volume of the excreta to be 
disinfected; let stand at least one hour, protected from flies. Masses 
are so difficult to penetrate that they should be broken up by stirring. 
It takes a carbolic acid solution some 12 hours to penetrate the in- 
terior of a fecal mass. 

The sputum may be burned or boiled. Strong carbolic acid, tri- 
cresol, or formalin are also applicable. 

The patient should have his own dishes, cups, spoons, glasses, etc., 
which should be scalded after each use. Eemnants of lunch, especially 
meat, milk, gelatin, broths, and other organic food in which the in- 
fection may live and even grow should not be eaten by others. Such 
remnants may be burned or first boiled and then discarded. Those 
who nurse the sick should keep out of the kitchen on account of the 
risk of contaminating the food. 

Towels, sheets, nightgowns, and all fabrics used about the patient 
should be disinfected either by boiling, or immersion for one hour in 
bichlorid of mercury, 1-1,000, carbolic acid, 2.5 per cent., or formalin, 
10 per cent. 

The water used to bathe the patient should be disinfected before 
it is allowed to run into the sewer. This may be done by adding suffi- 
cient carbolic acid or bleaching powder; the latter is cheapest and most 

Milk bottles must be kept out of the sick room. In any case, they 
should be scalded before returning to the dairy. 

The thermometer should be kept in formalin or other suitable ger- 
micidal solution. Eectal tubes, especially in hospital practice, must be 
carefully disinfected each time before using. 

The nurse must protect herself as well as others; a solution of bi- 
chlorid should be kept constantly at hand. Every time the patient is 
bathed, his mouth cleaned, or his buttocks washed, the hands must be 
disinfected and washed in soap and water. The nurse must exercise 
especial care if she is to go to the kitchen or to the ice-box, etc., as is 
frequently the case in private houses, where a special diet kitchen can- 
not be provided. The nurses, physicians, ward attendants, and others 
particularly exposed may protect themselves with preventive typhoid 
inoculations. The physician should be quite as careful as the nurse, 
not only so that he may not carry the infection to himself or other 
patients, but also that his practice may serve as a stimulating example. 

At the conclusion of the case a general terminal disinfection of 
the room and its contents may be practiced. This is best done with 
formaldehyde gas, followed by a general mechanical cleansing. 


Convalescents should not be given liberty until the danger of bacil- 
lus carrying has passed. This may be determined oidy by baeteriologic 
examinations of the stools and urine. Four successive negative results 
at intervals of several days are required before a conclusive report may 
be vouchsafed in the case of the stools. One examination of tlie urine 
is ordinarily sufficient. 

Tlie UFc of urotro))in (hexamethylenamin) diminishes the incidence 
of bacilluria, and is becoming a routine practice. 

Summary — Personal Prophylaxis. — The prevention of typhoid fever 
may be summed up in the word cleanliness — physical and biological 
cleanliness. By this is meant not only clean food, especially water and 
milk, but also cleanliness of person and environment. Typhoid fever 
has always prevailed where cleanliness is neglected and has diminished 
where it has been intelligently observed. It is true that typlioid bacilli 
do not breed in the rubbish and dirt of back yards and alleys, or in 
unkempt city lots, but these conditions in a city may be taken as an 
index of the general cleanliness of its inhabitants. 

The eradication of typhoid fever is easier in cities than in country 
districts; clean cities now have less typhoid fever than the surrounding 
rural region. Cities can well afford extensive and expensive sanitary 
works which are beyond the financial possibilities of sparsely settled 
districts. ]f a clean water from natural sources is not available, then 
large volumes of a polluted water may be rendered reasonably safe 
for municipal use by slow sand filtration or by bleaching powder. Fur- 
ther, cities can afford to inspect their milk supply and to supervise the 
pasteurization of all that is not safe. These two measures would prac- 
tically eliminate typhoid infection coming into cities in its food supply 
— especially if in addition to this a supervision is maintained over oysters 
and shellfish, and vegetables partaken in their raw state. Further, cities 
can well afford to employ skilled and experienced health officials and 
are financially able to engage the services of experts. On the other 
hand, each farmhouse represents, in miniature, all the problems with 
which the city deals by wholesale, and is often not financially able to 
meet its sanitary requirements. The country is the weakest link in 
our sanitary chain. Cities will find it a paying proposition to sup- 
press flies, rats, and other vermin, which may be done much more easily 
than in rural or suburban conditions. This should be done not only on 
account of the suppression of typhoid fever, but other diseases tlnis 
conveyed. The city beautiful must also be the city clean in its cellars, 
garrets, back yards, empty lots, alleys, and stables. 

To sum up, the main factors in the spread of typhoid fever in our 
large cities are: (1) water; (3) milk; (3) contact; (4) miscellaneous. 
In a city having a clean water supply the residual typhoid must be 
attacked along two definite lines, viz., improvement of the milk supply 


and its pasteurization, and a warfare against the disease in the light 
of an infection spread from man to raan. 

The health officer should establish a laboratory for the early diag- 
nosis of cases and for the discovery of carriers. The health officer 
should at once send a trained agent to every house from which a case 
of typhoid fever is reported. The visit should be made as early as 
practicable and with the object of seeing that the stools and urine are 
properly disinfected, patients isolated, milk bottles scalded, sick rooms 
screened, house placarded, visiting discouraged, and other necessary 
measures taken to prevent the spread of the infection. Convalescents 
should not be released until the absence of typhoid bacilli from the 
urine and stools has been demonstrated by four successive examina- 
tions. Carriers need not be indefinitely quarantined, but should be 
prohibited from engaging in any employment having to do with foods, 
or in which close personal contact, as in nursing, is required. Carriers 
should be instructed concerning the danger and educated to thoroughly 
wash and disinfect their hands, especially after a visit to the toilet. 
The health officer alone cannot eliminate typhoid fever from a city. 
He needs the help of the community. Much can be done through 
education. A stimulating leader may accomplish a world of good 
through voluntary effort, but in the end it requires comprehensive laws 
and an energetic enforcement of them, without fear or favor. 

The personal prevention of typhoid fever resolves itself into boil- 
ing the water, if suspicious; partaking only of milk or fresh milk 
products that have first been pasteurized, and otherwise assuring one- 
self that all food has been thoroughly cooked. In addition to this, 
direct and indirect contact with persons who have the disease, or who 
are known to be carriers, must be avoided. Sanitary habits should be 
encouraged, especially the one simple precaution of washing the hands 
before eating, and of keeping the fingers and other unnecessary objects 
away from the mouth and nose. In certain circumstances in which 
there is unusual exposure protection may be had by increasing immu- 
nity through typhoid inoculations. 


The prevention of cholera corresponds to the prevention of typhoid 
fever. In the case of cholera vigorous measures have been rewarded 
with signal success. It is quite possible to live in the midst of a raging 
cholera epidemic without contracting the disease. Within recent years 
epidemics have been suppressed and the spread of the infection limited. 

The home of true cholera is the delta of the Ganges, hence it is 
usually called "Asiatic cholera" to distinguish it from Cholera nostras 
or Cholera morlus. During the sixteenth, seventeenth, and eighteenth 


centuries cholera was epidemic at various times in India. It is only 
in the nineteenth century that cholera has spread along the routes of 
trade and travel to Europe (first in 1830), Africa, and America in 
1832. There have been four pandemics; one from 1817-1823, another 
1826-1837, a third 181G-1862, and a fourth from 1864-1875. In 1832 
it entered the United States by way of New York and Quebec and 
reached as far west as the military posts of the upper Mississipj)!. The 
disease recurred in 1835 and 1836, In 1848 it entered the country 
through New Orleans and spread widely up the Mississippi and was 
dragged across the continent by the searchers for gold all the way to 
California (1849). It again prevailed widely through this country in 
1854, having been introduced by immigrant ships into New York. In 
1866 and 1867 there were less extensive epidemics. In 1873 it again 
appeared in the United States, but did not prevail widely. In 1892 
the great epidemic of Hamburg occurred, and the disease threatened 
to become pandemic in Asia, Africa, and Europe. Cases were brought 
by transatlantic liners to New York, and a few cases occurred in the 
city, but its spread was prevented by aggressive measures. Cholera 
has prevailed for years in the Philippines, but is now under control. 
While the home of cholera is in the tropics, there is scarcely a country 
in the world that has not been visited some time or other by the ravages 
of this fatal disease. 

The incubation period of cholera is short, frequently 1 or 2 days, 
rarely over 5. The period of detention in quarantine is 5 days. One 
attack produces a mild grade of immunity which is not lasting. The 
disease is peculiar to man. 

The Cause and Contributing- Causes of Cholera.^ — The Vibrio cholerce 
or the "comma bacillus" of Koch is the undisputed cause of the dis- 
ease. The conditions of infection, however, are complex. Not everyone 
who takes the specific microorganism Ijv tlie mouth necessarily gets 
the disease, but without it there can be no cholera. Many cholera 
vibrios probably die in the acid juices of the stomach. There is, there- 
fore, perhaps less danger in taking small amounts of infection during 
active digestion than upon an empty stomach, for it has been shown ex- 
perimentally that cold drinks do not stay long in an empty stomach, but 
pass quickly through the pylorus. After the cholera vibrio has passed the 
pylorus and reaches the alkaline juices of the intestines, it may 
find ideal conditions for growth or may still have a hard struggle for 
existence. Here symbiosis must play a dominant role. It is well known 
in all cholera epidemics that a deranged digestion is an important pre- 
disposing factor to the disease. In the Hamburg epidemic a marked 
access of cases on Monday following the Sunday dissipations was noted. 
Raw fruits, crude fibrous vegetables, and other fermentable food, difficult 
of digestion, seem to favor the growth and multiplication of the cholera 


yibrio in the intestinal tract. In the light of this view raw fruits and 
vegitables may often be the predisposing factor rather than the medium 
v^hich conveys the infection. Just what the factors are that favor or 
^ndicap the growth of the cholera vibrio in the intestinal tract are 
undetermined. Pettenkofer stoutly maintained that the "comma bacil- 
lus" was only one of the factors in the etiology of the disease. He 
placed special importance upon the condition of the host and his en- 
vironment, and considered at least three fundamental factors in his 
X, Y, Z theory. X is the germ, Y the host or soil, Z the environment. 
In this connection disease may aptly be compared to fermentation, 
in which X represents the yeast, Y the carbohydrate, and Z the tem- 
perature, moisture, reaction, and other essential conditions for the 
growth and activity of the yeast. Pettenkofer maintained that X 
without Y and Z would not produce cholera, that is, while the cholera 
vibrio was pathogenic in India or Hamburg (1892), where Y and Z 
were favorable, it would be harmless in Munich, where Y and Z 
were unfavorable. To prove this theory, he and his assistant, Em- 
merich, drank pure cultures of cholera after first rendering the stomach 
contents alkaline. Pettenkofer, then an old man, had a diarrhea; 
Emmerich, on the other hand, had a sharp attack from which he almost 
lost his life. Similar convincing experiments have occurred among lab- 
oratory workers, who have accidentally gotten jjure cultures of cholera 
into their mouths. On the other hand, a number of persons who imi- 
tated Pettenkofer's experiment were not affected. Pettenkofer did not 
regard his own case as cholera, and insisted that the negative results 
lent confirmation to his theory of the importance of contributing factors 
(Y and Z). 

Diagnosis. — The diagnosis of cholera depends upon isolation and 
identification of the cholera vibrio in pure culture. This has become 
comparatively simple, but great care must be taken not to confuse the 
true vibrio of cholera witli a great host of other microorganisms which 
closely resemble it. 

A presumptive diagnosis of cholera may be made by finding large 
numbers of comma-shaped bacilli in direct microscopic examination 
of stained preparations, or in hanging drops of the mucous flakes 
ordinarily found in cholera stools. This test is only presumptive, the 
final criterion being the biological reactions of the microorganism ob- 
tained in pure culture. The two reactions which are specific and re- 
liable are Pfeiffer's phenomenon and agglutination. 

Dependence should not be placed upon morphological characters, 
cultural peculiarities, or pathogenicity upon laboratory animals, for 
these do not furnish the means of certainly defining the cholera vibrio. 
For the isolation of the cholera vibrio agar is preferable to gelatin, 
formerly so much used. The suspected material should be planted upon 


the surface of ordinary alkaline agar or upon Dieudonne's niedimn, 
using one of the small rice-like flakes or an equivalent quantity of 

Dieudonne's medium is prepared as follows: 

Sol. A. — Equal parts of a normal solution of potassium hydroxid 
and defihrinated ox-blood are mixed and sterilized in the autoclave. 

Sol. B. — Ordinary nutrient agar, exactly neutral to litmus. 

Seven parts of B are mixed with 3 parts of A and poured into 
Petri dishes. The plates should not be used immediately after their 
preparation. Dieudonne recommends keeping them several hours in the 
incubator at 37° C, uncovered and face down, or to heat them for 5 
minutes at 65° C. Equally good results can be obtained by keeping 
them 48 hours at room temperature. Tlie surface of the agar should 
be slightly dry. Once in condition, the plates should be used in a 
period not exceeding 5 or 6 days. 

Upon this medium cholera vibrios grow abundantly. On the con- 
trary, the organisms which most often accompany them on plate cul- 
tures, especially B. coli, grow either very poorly or not at all. 

When it is suspected that the cholera vibrios are few in number, 
they may be enriched by first planting in Dunham's solution. Ap- 
proximately 1 c. c. of fecal matter should be placed in 50 c. c. of the 
peptone solution. This is incubated at 37° C, and in from 6 to 8 
hours a loopful is taken from the surface and transferred to ordinary 
agar or Dieudonne's medium. Suspicious colonies are fished and studied 
further. A quick method of detecting carriers is given on page 108. 

Kolle and Gotchlich have shown from a large number of observa- 
tions that with strongly agglutinative serum, the power of which reaches 
1-4,000, the agglutinative power for common vibrios, not cholera, does 
not, as a general rule, exceed 1-50 and rarely reaches 1-200; agglu- 
tination in dilutions of 1-500 has been only very exceptionally ob- 
served. On the contrary, the true cholera vibrios agglutinate in dilu- 
tions varying from 1-1,000 and 1-20,000. Therefore, with a specific 
agglutinating serum having a titer of 1-4,000, any organism which is 
agglutinated in 1-1,000 may be considered true cholera. Organisms 
agglutinating in dilutions of 1-500 and 1-1,000 should be regarded as 

In any critical case Pfeiffer's reaction (see page 389) should be 
tried. This is specific. 

Modes of Transmission. — Cholera is spread by man from place to 
place. It follows the lines of trade and travel. Seaports are in- 
variably first attacked. The epidemic at Hamburg in 1892 was brought 
to that port by immigrants on board vessels from Russia. There are 
many similar instances. In 1849 many a gold hunter found another 
Eldorado than the one he was searching for, as cholera was dragged 


across the continent by the caravans seeking fortunes in California. 
The same thing takes place in the Indian pilgrimages to Mecca. 

The cholera vibrio enters the digestive tract through the mouth. 
It is taken in the food and drink. Infected water is a frequent me- 
dium of transference, and probably the sole vector of the great epi- 
demic outbursts. Cholera, however, may be transferred from man to 
man directly, also indirectly by flies, fingers, food, and all the innu- 
merable channels from the anus of one man to the mouth of another 
that have been described in the case of typhoid. 

In endemic or residual cholera, water-borne infection plays a minor 
role. This was well proven in the recent sanitary campaign against 
the disease in the Philippine Islands, in which the water was practically 
ignored and the disease conquered in the light of an infection com- 
municated rather directly from man to man. Cholera was spreading 
rapidly despite active measures. Its progress was stopped by throwing 
a sanitary corps across a narrow neck of land some miles in advance 
of the march of the disease. Here a quarantine was established and 
persons held 5 days under observation before they were permitted to 
pass. The usual disinfection and other measures were practiced and 
the disease effectively stopped. 

The cholera vibrio leaves the body in enormous numbers in the 
dejecta, also sometimes in the matter vomited. The cholera vibrio does 
not invade the blood and tissues generally, and, therefore, is not voided 
in the urine. Disinfection in this disease must, therefore, be concen- 
trated upon the discharges from the bowels and mouths, at the bedside. 

Water. — The cholera vibrio may live and even multiply in water. 
Koch in his original investigations found the organism in the foul 
water of a tank in India which was used by the natives for drinking 
purposes. It has been shown by experiment that the cholera vibrio may 
multiply to some extent in sterilized river water or well water; and 
that it preserves its vitality in such water for several weeks or even 
months. In recent times diolera organisms have been found not in- 
frequently in the water of wells, water mains, rivers, harbors, canals, 
and even sea water (the North Sea near the mouth of the Elbe), which 
have become contaminated with the discharges of cholera patients. It 
is plain from the nature of the ease that infected water must play a 
very large role in spreading this infection. 

The Broad Street Case in London. — The earliest and now classic 
instance in favor of the water-borne theory we owe to the late Dr. 
John Snow. This is the well known Broad Street pump outbreak in 
London in 18 54-, an account of which will be found on page 815. 

The best example of water-borne cholera is the Hamburg epidemic 
of 1892, which I was fortunate enough to see in part. In this case 
no link in the chain of evidence is missing. Cholera was brought to 


Hamburg by immigrants either from Russia or France. The water 
of the Elbe was infected with their discharges. The Vibrio choleroe 
was readily isolated from the river water wliich was distributed through- 
out the city for drinking purposes without purification. The sewers of 
Hamburg emptied into the river Elbe near the water intake, which 
produced an increased concentration of the infection. An account of 
the epidemic will be found on page 819. 

Other Modes of Transference. — The fact that water-borne in- 
fection is practically the only cause of the large cholera epidemics 
must not overshadow the importance of other modes of transmission. 
In addition to tlic violent outbreaks, cholera occurs in nests or smoul- 
ders like endemic typhoid. It is difficult to trace the connection be- 
tween cases in endemic areas. Thus, a careful study of the cholera 
situation in Manila disclosed the fact that isolated cases would crop 
up at widely different points without any evident connection hetween 
them. Cholera carriers were suspected but not proved in this instance. 
At irregular intervals of several years the disease would gather force, 
and cases multiply, until it assumed epidemic proportions, it is be- 
lieved entirely independent of the water supply. The way cholera was 
dragged across our continent by the "forty-niners," and its occurrence 
among the Mecca pilgrims, are instances of its spread largely inde- 
pendent of infected water. 

Contact Infection. — Contact infection in cholera must not be 
underestimated. Persons frequently become infected by handling the 
dejecta or through freshly infected fomites, such as soiled linen. Di- 
rect transmission from person to person is not infrequent among physi- 
cians and nurses. In congested quarters, where many persons live un- 
der uncleanly conditions, contact infection plays an important part. 
The same thing may be seen on board vessels, in which case the dis- 
ease may be confined to the firemen, stewards, or some other limited 
group who are required to live in close contact with each other. Epi- 
demic outbreaks due to contact infection have been recorded, such as 
the 30 cases which occurred in the fall of 1892 in Boizenburg. 

Cholera is not highly "contagious," for physicians, nurses, and 
others in close contact with patients need not become infected pro- 
vided intelligent measures are adopted. On the other hand, there is 
great danger of tlie spread of the disease through devious and hidden 
routes, as is the case with typhoid and dysentery. Washerwomen and 
those who are brought in very close contact with the linen of cholera 
patients or with their stools are prone to contract the disease. Koch, in 
his original investigations, found that the "comma bacillus" may mul- 
tiply rapidly upon the surface of moist linen. 

Milk may be contaminated, but is probably not a frequent medium 
of infection, for the reason that its acid reaction is inimical to the 



cholera vibrio. Green vegetables and fruit that have been washed in 
an infected water may convey the disease. The bacilli live on fresh 
bread, butter, and meat for from 6 to 8 days. 

Flies, Etc. — It has been shown that the cholera vibrios may live in 
the intestines of flies for at least 3 days, and these and other insects may 
also spread the infection mechanically. The cholera vibrio is a frail 
organism and dies rapidly when dried or exposed to light and other 
injurious influences. Infection through the air is, therefore, not to be 
dreaded. Fomites, such as bed and body linen or other objects, including 
floors, walls, toys, etc., contaminated with the dejecta, can be regarded as 
possible sources of infection. There is, however, a special limitation 
in this case, owing to the fact that this organism is so readily de- 
stroyed by desiccation and crowded out by saprophytic microorganisms. 
Thus, as a rule, only fresh dejecta and freshly contaminated objects 
are liable to convey the infection. 

Bacillus Carriers. — The cholera vibrios are passed in the feces 
during the early part of the disease. They usually disappear after 
the fourth to the fourteenth da}", but may remain a much longer time. 
The following are the longest cited by Pf eiff er : ^ 

persistence of cholera vibrios in stools of convalescents, or 

BACILLUS carriers 

Name of Observer. 

Name of Observer. 





Lazarus and Pulicke 







Abel and Clausen 




McLoughlin found bacillus carriers numerous in epidemic centers. 
Thus he found 6 to 7 per cent, of carriers among healthy individuals 
living in the infected neighborhoods in Manila. On the other hand, 
carriers were exceedingly rare in neighborhoods having few cases. 
Persons in good health may harbor the cholera organism in their in- 
testines. Cholera carriers, therefore, play a similar role to typhoid car- 
riers in spreading the infection. Less, however, is known concerning 
cholera carriers than typhoid carriers. 

Several different methods for the detection of cholera carriers are 
applicable. All of them are based upon the facility with which the 
vibrio grows upon Dunham's solution. Particles of feces are planted 
in this medium and subsequently examined for comma-shaped mi- 
croorganisms. If found, the diagnosis is presumptive. Pure cul.- 

^ Hygienische Eundschau, February, 1910, Vol. XX, No. 4. 


hires should then he made and studied for agglutination. See page 

The routine bacteriological examination of immigrants from cholera- 
infected ports, as practised at the Quarantine Station at New York, 
in 1912, was as follows:^ 

1. Inoculation of feces into Dunham's peptone solution (at 37° C). 

2. Subinoculation at the end of six hours of one loop of the sur- 
face growth into a second Dunham's peptone tube. 

3. Examination of a smear taken from the surface growth of the 
second Dunham's peptone tube, after it has been incubated six to nine 
hours at 37° C. 

Bendick uses a modified Dunham's solution containing sodium car- 
bonate, 1 gram; saccharose, 5 grams; and phenolphthalein solution, 
5 c. c, in addition to the usual amount of water, peptone and salt. The 
cholera vibrios ferment the saccharose ; the acid produced unites with the 
sodium carbonate and the medium becomes neutral, hence the red color 
of the phenolphthalein disappears. 

Immunity and Prophylactic Inoculations.— The immunity produced 
by an attack of tlie disease is of short duration. Attempts have 
been made to produce an artificial immunity by the injection of cholera 
cultures. These were first made by Ferran of Spain in 1884, but 
the cultures used by him obtained directly from cholera stools were 
not pure. Haffkine tested the method on a large scale in India; over 
40,000 persons were inoculated with attenuated cultures up to 1895. 
Haffkine proceeded in accordance with the well known methods of 
Pasteur in anthrax, by using two vaccines of different strengths. 
The first was obtained by growing the culture at a heightened tem- 
perature, which produced a very attenuated strain. The second con- 
tained living vibrios weakened by passage through guinea-pigs. The re- 
actions produced were generally slight in degree and consisted of a brief 
elevation in temperature, headache, malaise, as well as redness, swell- 
ing, and pain at the site of injection. The results were not clear cut 
on account of the difficulty of comparing the disease in the inoculated 
with suitable controls. However, the general impression is that the 
method has some prophylactic value. This opinion has been confirmed 
by the later work in various parts of India, where, up to the year 
1899, of 5,778 inoculated persons, only 27 had cholera and 14 died, 
whereas, of 5,549 non-inoculated, 198 had cholera, of which 124 died. 
Kolle showed that the blood serum of the inoculated persons contains 
a specific bacteriolysin similar to that contained in the blood serum 
of those who have recovered from the disease. Kolle uses 2 mg. of 
an agar culture suspended in 1 c. c. of physiological salt solution and 
killed at 58° C. for one hour for the first injection, and twice this 
•Bendick: Jour, of Am. Pul). Health Assn., I, No. 12, 906, Dec, 1911. 


dose (4 Tag.) for the second; 0.5 per cent, of phenol is added as a 
preservative. The immunity produced by these protective inoculations 
lasts a long time, but after a year the specific antibodies begin to 
diminish in the blood serum. 

There seems to be little doubt in Japan concerning the value of the 
protection afforded by the inoculation of dead cultures;, for in the 
district of Hiogo, during the epidemic of 1902^ 77,907 persons were 
inoculated. Of these 47, or 0.06 per cent., took cholera, and 20, or 
0.02 per cent, died, whereas, among 825,287 persons not inoculated, 
1,152, or 0.13 per cent., took the disease, and 863, or 0.1 per cent., 
died. It is especially noteworthy that all the cases among the inocu- 
lated group were in those who received an injection of 2 mg. of the 
dead culture. Later 4 mg. were used, and in this group no cases oc- 

Protective inoculations as a proph3dactic measure against cholera 
will never be popular or necessary in communities with sufficient sani- 
tation. It may, however, be of value in camps, armies on the march, for 
physicians, nurses, ward tenders, and others especially exposed. 

Quarantine. — Cholera is an infection which fully Justifies maritime 
quarantine practice. The disease may be blocked by a careful system 
of inspection, detention, and disinfection at the seaport. In order 
for maritime quarantine to be effective for cholera, it must have the 
assistance of a bacteriological laboratory to diagnose cases and recog- 
nize carriers. A strict watch must be kept for mild and ambulant 
cases of the disease. 

In the summer of 1912 the quarantine authorities at the large sea- 
ports on our Atlantic littoral examined about 34,000 specimens of 
bowel discharges from passengers and crew from cholera-infected ports. 
At the New York quarantine the cholera vibrio was isolated from 28 
persons sick with the disease, and 27 healthy persons were found to be 
discharging vibrios in their feces. These carriers could not have been 
discovered except by laboratory examination. Seven cases of cholera 
were detected at other ports by the same methods. There can be no 
doubt that the adoption of this measure kept cholera out of the 

The Foreign Inspection maintained by the United States Govern- 
ment during the epidemic of 1892-93 was a convincing demonstration 
of the value of this service as one of the safeguards against cholera. 
Officers of the Public Health and Marine Hospital Service stationed 
at foreign ports supervised the water and food supply of the depart- 
ing vessels, inspected the crew and passengers as to their health; those 
coming from infected localities were detained under observation 5 
days before they were permitted to embark. On practically none of 
the vessels complying with these requirements did cholera appear. 


whereas it broke out comparatively frequently on vessels which did 
not comply with the restrictions, but sailed from the same ports under 
similar conditions. A similar experience demonstrating the value of a 
sanitarv inspection of vessels leaving an infected port was demonstrated 
in the Philippines, where, since the American occupation, cholera has 
been kept off the returning transports and its interisland spread has 
been checked by a sanitary supervision of vessels at both the ports of 
departure and arrival. 

Personal prophylaxis requires, first of all, scrupulous cleanliness on 
the part of the pcr.-on and iiis surroundings. Those who handle cholera 
patients, their dejecta, or infected articles must carefully disinfect their 
hands each time, and should under no circumstances eat or drink any- 
thing in the sick room. During cholera times all water and food of 
every description should be boiled or thoroughly cooked just before 
it is partaken of. Great care must be exercised that the water or food 
does not become infected after it has been boiled or cooked. The usual 
measures should be taken to guard against flies and other vermin. 
With strict attention to these measures, it is possible to avoid the in- 
fection. In addition, however, attention to general hygiene and espe- 
cially to the character of the food and regularity of meals should be 
given. Slight attacks of indigestion and diarrhea should receive prompt 
medical attention. 

Summary — Prevention. — Preventive measures should first of all 
be focused upon the cholera cases in order to prevent the spread of the 
infection at the bedside. This includes early and controlled diagnosis. 

Cholera patients should be cared for in special hospitals where all 
these necessary measures may be carried out by trained assistants. The 
infection in cholera stools may be destroyed with formalin (10 per 
cent.), carbolic acid (5 per cent.), milk of lime (1 to 8), or chlorinated 
lime (3 per cent.). 

Persons leaving a cholera region should either be detained in quar- 
antine for 5 days or be watched this length of time after arrival at 
the place of destination. This m.ay be accomplished by requiring them 
to report twice daily to the sanitary authorities. It is unnecessary to 
disinfect merchandise shipped from a cholera town. 

For the control of a cholera outbreak it is important to require that 
all cases, as well as all suspicious cases, be reported. A bacteriolog- 
ical laboratory is necessary to confirm the diagnosis and arrangements 
must at once be made to isolate the cases and to disinfect the dejecta, 
the body and bed linen, and other materials. Convalescents are not 
released until two successive examinations at 5-day intervals show the 
absence of the cholera vibrios. 

On account of the frail character of the vibrio a general disinfec- 
tion of the house is not necessary in cholera. The room itself may 


be treated with formaldehyde or the surfaces washed down with a bi- 
chlorid solution or one of the alkaline coal-tar creosotes. The water- 
closets may be disinfected with formalin, carbolic acid, milk of lime^ 
or chlorinated lime. Sjjoons, cups, saucers, and remnants of food 
should be treated as in the case of typhoid. Otherwise the preven- 
tion of cholera is a strict counterpart of that of typhoid. 

A summary of the preventive measures necessary to control an out- 
break of cholera are : centralization of authority in one person ; estab- 
lishment of a system of securing and reporting information; organiza- 
tion of the personnel for the sanitary* work ; enactment of necessary 
ordinances; house to house inspection; safe disposal of feces of entire 
population; provision for a safe water supply; supervisory control of 
food and drink:; a search for, anjl control of carriers; isolation and care 
of patients in special hospitals; separate hospitals or wards for suspects; 
a laboratory; detention camps or barracks for those desiring to leave 
the infected area; disinfection, etc. For further discussion concerning 
the control of epidemics, see page 319. 


Classification. — For the purpose of prevention we may consider all 
dysenteries under three heads: (1) bacillary dysentery, (2) amebic 
dysentery, (3) symptomatic dysentery. 

Bacillary dysentery is an acute infectious disease caused by the 
B. dysenterioE, an organism that closely resembles the typhoid bacillus 
in cultural resp.ects. It differs from typhoid in that it has limited or 
no motility. More fundamental differences are found in its biological 
properties, such as specific agglutination and pathogenic power. There 
are at least two well recognized types of B. dysenterice. One corre- 
sponds to the original organism discovered by Shiga in 1897 in the 
Japanese epidemic, and the other to that found by Flexner in Manila. 
The Shiga bacillus does not ferment mannite, while the Flexner feiTnents 
that "sugar" with the production of acid. Further, the two organisms 
differ in their properties of agglutination toward specific sera. A very 
strong endotoxin may be extracted from the Shiga type which, when 
injected intravenously into rabbits, produces a fatal intoxication with 
a faithful reproduction of the symptoms and lesions of bacillary dysen- 
tery. Kraus and Dorr and also Todd have found that the Shiga strain 
produces such a soluble toxin, which is not the case with the Flexner 

Amebic dysentery results from infection with the Entamoeha hys- 
tolytica. There are marked differences" between the amebic and the 
bacillary types of the disease. The former is a chronic infection which 
starts insidiously, is characterized by relapses and recurrences^ is fre- 


quently associated with sequelae, such as liver abscesses, and occurs 
sporadically or in endemic foci, mainly in the tropics. Epidemic out- 
breaks of the amebic form of dysentery are not known. Bacillary 
dysentery, on the other hand, is an acute febrile disease, usually self- 
limited, with marked symptoms of toxemia, sudden onset, no sequelae, 
and occurs in widespread and severe epidemics. The bacillary disease 
occurs in the temperate regions as well as in the tropics, and is almost 
always the cause of dysentery outbreaks in ships, camps, jails, etc. The 
lesions of the two diseases also differ markedly. In amebic dysentery 
the ulcers arc undermined, whereas in the bacillary disease the inflam- 
mation is diffuse and of varying grades of severity, which may reach 
coagulation necrosis or gangrene. There are also notable differences in 
tlie treatment; for example, ipecac given early or rectal injections are of 
service in amebic dysentery, but are of questionable use and may even 
do harm in the bacillary form. So far as prevention is concerned, how- 
ever, both diseases may be regarded as intestinal infections entering by 
the moutli, and therefore the prophylaxis is practically the same and 
corresponds closely to that of typhoid or cholera. 

Under symptomatic dysentery are grouped all other conditions with 
dysenteric symptoms resulting from a great variety of causes. 

Modes of Transmission. —The dysentery bacillus enters the body by 
the mouth and leaves the body in the alvine discharges. So far as 
known, the dysentery bacillus does not penetrate deeply into the tis- 
sues, and is seldom found in the circulating blood. It therefore does 
not appear in the urine. 

The infection is transferred from man to man directly or in- 
directly in precisely the same ways described for typhoid. Undoubt- 
edly drinking water frequently contains the infection, and well marked 
water-borne epidemics have been reported in recent years, particularly 
in Japan. Contacts, food, and flies also play an important role. The 
epidemiology of bacillary dysentery is about the same as that of typhoid. 
It is largely a summer disease. In wars it used to cause great ravages; 
as in the Crimean war, our own civil war, the Franco-Prussian 
war, and the recent Russian-Japanese war. Overcrowding, lack of 
cleanliness, and other unhygienic conditions favor the spread of bacil- 
lary dysentery, so that it is sometimes called famine, asylum, ship, 
or jail dysentery. The mortality varies greatly, from 6 or 7 to 26 
or 30 per cent. Bacillus carrying in dysentery occurs, and probably 
plays a more important part in spreading the disease than we now 
suspect. As a rule, the bacilli soon disappear from the stools in the light 
cases, but Shiga has found them more persistent in some instances, 
von Drigalski reports an outbreak in Germany caused by a, returning 
soldier. Recent convalescents are particularly apt to spread the infection. 

The 3ntamocba liystolytica is also taken in by the mouth and 


passed by the bowels. It probably exists in its free living state in 
water, upon vegetables and fruits, and other moist surfaces. There is 
some suspicion that the buds of the entameba may be carried by the 
air. There are still large lapses in our knowledge concerning the 
free living stages, and other facts in the life history of the ameba, so 
that our preventive measures lack finality. 

Resistance. — The dysentery bacillus has about the same resistance 
to germicides and other unfavorable conditions as the general class 
of spore-free bacteria. It dies in about 8 to 10 days when dried. It 
may live for months when moist. It is sensitive to acids. Phenol, 
0.5 per cent., kills the dysentery bacillus in 6 hours, 1 per cent, in 
30 minutes, 3 per cent, in 1 to 2 minutes. Bichlorid of mercury, 
1-1,000, kills it at once, and direct sunlight in about one-half an hour. 
I have found certain strains of the dysentery bacilli somewhat more 
resistant to heat than the typhoid bacillus. They are killed with cer- 
tainty at 58° C. for one hour, or at 60° C. for 20 minutes. The dysen- 
tery bacillus resists cold and may live for months when frozen. 

The Entamceha hystolytica is probably less resistant to heat and 
germicides than the B. dysenierice. Our knowledge concerning the 
effects of drying, sunlight, and other deleterious influences is still un- 

Immunity. — The susceptibility to dysentery varies greatly. This is 
doubtless due in part to the bacterial flora of the intestinal tract as 
well as the conditions of the intestinal mucosa. Symbiosis must play 
a very important role either in permitting or hindering the dysentery 
bacillus to grow in the intestinal tract. There is still a qiiestion whether 
a true immunity is acquired by one attack of bacillary dysentery. This 
seems probable, although it is not unusual for a j)erson to have two or 
more attacks of dysentery in one season. Kolle looks upon this as an 
exacerbation of a chronic type brought on by errors of diet, exposure, 
etc. The experiments on animals indicate that dysentery probably 
belongs to that group of diseases which leave a certain amount of pro- 
tection after one attack. A definite and high grade of immunity can 
be produced experimentally in several of the lower animals. Upon this 
question, however, we need light. Horses may be immunized to a high 
degree, and their sera contain a certain amount of antitoxin and other 
antibodies. This serum has been used in treatment, but has no par- 
ticular value as a preventive. There is evidently no immunity in 
amebic dysentery. 

Personal Prophylaxis. — To avoid dysentery the two essentials are: 
scrupulous cleanliness and the boiling of all water and cooking of all 
food that passes the mouth. The usual precautions against flies and 
vermin, and care as to personal hygiene, especially diet, are indicated. 

Bacillary dysentery is a common disease in infants, and it would be 


a wise precaution to consider all cases of infantile diarrhea as infectious 
and to take precautions accordingly. 

Dysentery should he included in the notifiahle diseases and laboratory 
aid furnished by the Board of Health to assist diagnosis. Cases should 
be isolated in the same sense that cases of typhoid are isolated and dis- 
infection practiced at the bedside. Outbreaks in institutions should 
always be investigated and vigorous measures taken to check further 
spread and to prevent recurrences. In all respects the prevention of 
dysentery is a close parallel to that of typhoid. 


(Uncinariasis or Anchylostomiasis) 

Theoretically the prevention of hookworm disease is comparatively 
simple, for here we have an infection of which we know the parasite 
and its life history, its mode of exit and entrance into the body, and 
we possess a satisfactory cure for the disease within reach of all. Prac- 
tically, however, we have ignorance, apathy, poverty, and uncleanliness 
to deal with before satisfactory prevention, much less eradication, can 
be achieved. It is now plain that hookworm disease presents a sani- 
tary problem of first magnitude, not alone in our southland, but in 
practically all tropical and subtropical countries. Further, there is a 
large economic and industrial aspect to this question in medical biology. 

Distribution. — Hookworm disease encircles the globe in the tropical 
and subtropical climes; it diminishes toward the temperate regions. 
It is not endemic in the colder latitudes, except in mines, especially those 
of Wales, Germany, Xetherlands, Belgium, France, and Spain. The 
infection belts the earth in a zone about 66° wide, extending from 
parallel 36 north to parallel 30 south latitude. The amount of infec- 
tion is great in American Samoa, where it is found in 70 per cent, 
of the population; in the southern two-thirds of China, in 75 per cent, 
of the population; in India from 60 to 80 per cent, of the 300.000.000 
population have the disease; in Ceylon, 90 per cent, in many parts; 
in Xatal, 50 per cent, of the coolies on sugar and tea estates ; in Egypt, 
50 per cent, of the laboring cla^s; in Dutch Guiana, 90 per cent, in 
many parts; in British Guiana. 50 per cent, of all; in Co- 
lombia, 90 per cent, of those living between sea-level and 3,000 feet, 
which includes most of the population; in 1904 the Porto Rican Anemia 
Commission found that 90 per cent, of the rural population of Porto 
Rico were infected. Stiles estimates that in this country 2.000,000 in- 
dividuals have the infection from the Potomac to the Mississippi, along 
the Atlantic littoral and the Gulf states. In some German mines from 



( ) 

Fig 14. — H o o k - 

WORMS, Natural 

30 to 80 per cent, of the miners have been found to be infected. Gunn ^ 
has shown that from 50 to 80 per cent, of those working in the Cali- 
fornia mines are infected. It is probable that all the older mines em- 
ploying foreign laborers sooner or later become endemic 

In 1879 an outbreak of hookworm disease (miner's 
anemia) occurred among the laborers in St. Gotbard"s 
tunnel. This aroused the interest of the whole scien- 
tific world. The polluted soil of the tunnel was found 
to be impregnated with the eggs and larvae. Interest in the disease in 
this country was aroused through the work and enthusiasm of Stiles. 
Varieties of Hookworm. — Almost all mammalian animals 
have hookworms, but each host species has a different kind of 
hookworm; that is, the hookworms of the dog, fox, horse, the 
seal, etc., differ from each other, and are specific. The hook- 
worm of the dog will not infest man or other mammalian host; 
the hookworms of man do not develop to maturity in the lower 
animals, etc. 

Two species of hookworm are found in man — the old world 
form (Anchylostoma duodenale), and the new world form 
(Necator americanus) . The distinction between these two 
worms has a zoological rather than a practical bearing, for both 
produce the same symptoms, require the same treatment, have 
the same life history, and call for the same preventive measures. 
The chief differences between these two hookworms consist in 
the fact that the old world form has one pair of ventral hooks, 
two conical dorsal teeth, and the posterior ray of the caudal 
l)ursa divides two-thirds its way from the base, and each divi- 
sion has three tips (tripartite). The new world form has ven- 
tral lips, a dorsal median tooth, and one pair of dorsal and one 
pair of ventral lancets deep in the buccal cap- 
sule. The posterior ray of the caudal bursa 
divides at its base and each division has two tips 

According to Stiles, the vast majority of cases 
of hookworm disease in man in the United States 
are due to the new world form (Necator ameri- 

Modes of Transmission. — The usual mode of 

transmission, perhaps in 90 per cent, of the cases, 

is through the skin. The infection may also be 

taken by the mouth in drinking water or soiled 

food, or from contaminated objects, such as dirty fingers. It has been 

^Jour. A. M. A., Vol. LVI, No. 4, Jan. 28, 1911, p. 259. 

Fig. 15.- 

-HooKWOEM Em- 


shown by experiment that animals can be infected by drinking water 
containing the embryos. While this source of infection plays a minor 
role, it is not to be disregarded. 

The infection leaves the body exclusively in the feces, which con- 
tain the eggs of the parasite. 

The Parasite. — For a correct understanding of the prevention of 
hookworm disease it is necessary to have a knowledge of the essential 
features of the life history of the parasite. 

Hookworms are round worms (nematodes) belonging to the sub- 
family Uncirmnince. The adult worm is about one-half to three-quar- 
ters of an inch long, and about the diameter of a wire hairpin. 

The adult hookworm lives in the intestinal tract, usually in the 
small intestine. It attaches itself to the intestinal wall, wounds the 
mucosa, sucks blood, eats the epithelium, and probably produces a toxic 
substance which injures the host. 

The female worm lays a prodigious number of eggs in a never- 
ending stream, which pass from the host in the feces. The embryo 
does not mature within the egg except in the presence of oxygen. Hook- 
worm embryos, therefore, do not undergo full development until the 
eggs are discharged into the outer world. On the other hand, the eggs 
of Strongyloides stercoralis, the parasite of Cochin-China diarrhea, con- 
tain fully developed embryos in the freshly passed feces. The hook- 
worm embrj'os become mature within the egg in 6 to 8 hours in the 
presence of moisture, warmth, and oxygen. It is, therefore, necessary 
to examine the fresh stools in order that this difference between the two 
infections may be of value in differential diagnosis. 

Under favorable conditions the embryo escapes from the egg and 
becomes a larva in about 24 hours. This free-living larva exists and 
moves in moist soil and feeds upon the organic matter found there. 
In the course of two days or more the larva sheds its skin (ecdysis) 
and thus passes to the first molt. The larva continues as a free-living 
parasite, and in about a week again sheds its skin, but now continues 
to live encysted inside this discarded skin. This is the second ecdysis 
and this encysted larva no longer takes food. This stage in the life 
history of the parasite is of special importance for the reason that it 
is capable of piercing the skin; that is, it is the infecting stage. In 
this condition the parasite may live in a dormant condition for five 
months, perhaps longer. 

The hookworm larva passes in all through five ecdyses or molts. 
Two of them occur during its free-living stage and three of them 
during its residence in the host. With each ecdysis the larva approaches 
more nearly the appearance and structure of the adult worm. 

The larva has a slow motion and under favorable conditions prob- 
ably travels a number of yards, increasing the radius of soil pollution. 


The larva pierces the skin and passes by a circuitous route to the 
intestinal tract. The parasite may enter the skin at any place, but it 
usually goes through the soft and thin skin between the toes. In its 
passage through the skin the larva produces an inflammatory reaction 
(ground-itch) which results partly from the irritating action of the 
presence of the foreign body, but mainly from the bacteria carried 
along with the larva. These primary lesions may consist of a few 
itching papules or pustules to a severe dermatitis. Of 4.741 patients 
questioned by Ashford, King, and Gutierrez in Porto Eico, 4,664, or 
about 98 per cent., gave a history of ground-itch, which is now recog- 
nized as the first stage of the disease. 

The fact that the infection with hookworm disease is usually con- 
tracted through the skin was discovered by Looss in Cairo, Eg3'pt. He 
also unraveled the course of the parasite from the skin to the intes- 
tines. This brilliant discovery, which is one of the romances of med- 
ical biology, is the foundation upon which prevention against the in- 
fection depends. In 1895 Looss accidentally spilled a drop of water 
containing many larvge upon his hand, and noted that they disappeared, 
leaving their delicate sheaths behind them. Seventy-one days subse- 
quently he developed intestinal uncinariasis. The experiment was then 
repeated upon a volunteer, and hookworm eggs appeared in his stools 
in 74 days. Claude Smith found eggs in the feces 6% weeks and 7 
weeks after experimental skin infection on two persons with the Amer- 
ican parasite (Xecator americanus). 

The wanderings of the parasite from the skin to the intestine were 
worked but by Looss partly by placing larvae upon an amputated leg 
and also by studying the question upon puppies. The hookworm larva 
usually pierces the skin through a hair follicle, enters the subcutaneous 
tissue, and then finds its way through the lymphatics to the neighbor- 
ing lymph nodes. The larvae are able to squirm through the lymph 
nodes, pass to the thoracic duct, and thence to the vena cava and the 
right heart. From the right heart they are carried in the blood stream 
to the lungs. The larva are too large to pass the capillaries of the 
lungs. They pierce the capillar}^ walls and appear in the alveoli and 
are now, to all intents and purposes, again in the outer world. They 
pass up the bronchi and trachea to the throat, whence they are swal- 
lowed, and finally lodge in the small intestines. During their travel 
through the body they pass through three ecdyses. 

The adult worm attaches itself to the mucous membrane by means 
of the powerful buccal lancet. The epithelium is drawn into the buc- 
cal cavity as though by a powerful suction. The worms are usually 
found in the small intestine, especially in the jejunum, less often in 
the duodenum, and rarely in the ileum and lower reaches of the in- 
testinal tract; they are occasionally met with in the stomach. 


The parasites imbibe large amounts of blood, some of which passes 
through the worm unaltered. Tlie wound continues to bleed after the 
worm releases its hold, owing perhaps to a hemolytic substance in the 
mouth parts of the parasite. The worm does not remain fastened 
to one place indefinitely, but releases its hold and attaches itself anew. 
This produces numerous minute wounds, favoring secondary infections. 
The hookworm probably produces a poison which is absorbed and which 
accounts, in part, for the anemia and other symptoms of the disease. 
The severity of the symptoms bears no definite relation to the number 
of worms. The number varies greatly in individual cases; from one 
or two to thousands. Sandwith counted 250 worms and 575 bites in 
one case; 2,000 are not an uncommon number. The Porto Rico Com- 
mission counted as many as 4,000 passed by one individual. 

Immunity. — There is no acquired immunity to this disease. There 
is, however, a definite racial immunity, as shown by the negroes and the 
Filipinos, who are often infected but have comparatively slight symp- 
toms. Stiles found that in this country the negro is the great reser- 
voir for hookworm disease in that he is frequently infected but slightly 
affected. Perhaps the negro has had the disease so many generations 
in Africa that he has become immune. It is conjectured that the in- 
fection was brought to America through the negro slave trade. Hook- 
worm disease lowers resistance and greatly increases the chances of 
other infections, especially tuberculosis. The secondary results are often 
more disastrous than the primary effects. 

Resistance of the Parasite. — The adult worm in the intestinal tract 
may be benumbed or killed with thymol, betanaphthol, chloroform, 
gasoline, eucalyptus oil, and other of the usual vermifuges. 

From the standpoint of prevention, it is more important to know 
the resistance of the eggs and larvae during their free-living stages. 
Stiles and Gardner have shown that the soil under and around privies 
is not entirely free from infection with hookworm even five months 
after the privy was last used, although the infection is considerably 
reduced at tlie end of four months. When the fecal matter has un- 
dergone decomposition under water most of the hookworm eggs are 
dead in about ten weeks, though some still survive, but probably all 
are dead in three months. It would not be safe to use such material as 
a fertilizer in less than three months. The larvae may live in water 
at least thirty days. The encysted stage is most resistant, surviving 
five months; perhaps longer. 

The larvag are readily killed by dryness and freezing. The infec- 
tion was once considered to be dust-borne, but the fact that the para- 
sites are killed by drying renders the danger from dust negligible. 
The fact that freezing kills the larvae largely explains why the disease 
is not endemic in this countrv north of the Potomac. 


It has been shown that chlorinated lime fails to kill hookworm 
eggs in 22 to 40 hours. Schiiffler kept the larvae alive almost four 
months in water with two or three drops of a one per cent, quinin 
solution to 10 c. c. Oliver found that sea water killed the larvae in 37 

Prevention. — The prevention of hookworm disease consists in pre- 
venting pollution of the soil and in treating existing cases so as to 
diminish the amount of infection. The principles of prevention are 
easy in theory, but their application is difficult in practice on account 
of the widespread and enormous amount of the disease. The suppres- 
sion of hookworm disease means the social and economic uplift of na- 
tions, the education of millions of people, and an entire change in their 
daily hygienic habits. Education of the masses is an important factor;, 
calling for cooperation between the health authorities, civic forces, the 
medical profession, schools, and philanthropic agencies; it is something 
for the preacher and teacher. 

Soil Pollution. — The prevention of soil pollution is the essential 
factor; it is the key to the situation. This one line of prevention 
would blot hookworm disease out of existence. This requires the build- 
ing of proper privies, and insisting upon their being used in country 
districts. In warm countries direct pollution of the soil is much more 
common and also much more dangerous than in cold countries. Add 
to this the custom of going barefooted and we have all the factors neces- 
sary for the dissemination of hookworm infection. 

Stiles estimates that 68 per cent, of the rural homes in the South 
are without privies. Even some schools do not have these accom- 
modations, and are, therefore, hotbeds of infection. For the care and 
disposal of night soil see chapter on sewage. 

The Eradication of the Infection in Man. — Hookworms may 
be expelled from the intestinal tract by the use of thymol, betanaph- 
thol, or other anthelmintic. The eradication of the infection through 
the treatment of all infected persons is an essential factor in preventive 
measures. The usual treatment is as follows : Saturday evening a 
full dose of magnesium sulphate or other purge is given to permit 
direct access of the thymol to the worms, which are often imbedded in 
the mucus or chyme. The object is to treat the parasite and not the 
host. On Sunday morning, at 8 o'clock, 2 grams (30 grains) of thy- 
mol, for an adult, finely powdered in capsules, are given by the mouth. 
Two hours later, at 10 o'clock, 2 more grams are administered; and at 
12 o'clock another dose of salts. During the treatment it is impor- 
tant to avoid alcohol, fats, and oils, as thymol is soluble in these sub- 
stances and they are, therefore, dangerous, as they thus favor absorption. 
The treatment is repeated every Sunday until the eggs disappear. One 
treatment usually suffices. The Porto Eican Commission sometimes 


found it necessary to use two, three, four, and up to eleven treatments. 

The eradication of the infecti&n in man was carried out on a 
wholesale scale by the Porto Rican Anemia Commission, consisting of 
Ashford, King, and Gutierrez. Their methods were highly successful 
and will doubtless serve an equally useful purpose in other places. 
They established a clinic for the microscopic diagnosis and free treat- 
ment of the disease. The good results of treatment spread rapidly, 
so that the facilities of the clinic were soon taxed to its utmost capac- 
ity. Not the least important function of the clinic was to educate 
the profession qs well as the people. In a little while the clinic was 
moved to another point, and so on, until it gradually covered the entire 

Education. — Education is one of the most important factors in 
eradicating hookworm disease, for the reason that its final control de- 
pends upon improvements in the sanitary habits of the people, espe- 
cially in the rural districts. To change the daily habits of half a na- 
tion is an uplift that requires time and patience. It is perhaps best 
to begin with the school children; even then it will take a generation 
for results. Very little can be accomplished by force, and, if the 
customs and prejudices of the people are ignored, the reformer and 
benefactor meet with rebuff and failure. It is a good idea to have 
a public health day or a public health week in the schools, during which 
time lectures and educational work upon hookworm, typhoid, tubercu- 
losis, and other prevalent infections are considered. The children carry 
the lesson into the home. Pamphlets, posters, lectures, exhibits, and 
popular articles in the magazines and newspapers all contribute their 
share. The medical profession in the infected areas may need in- 
struction and a little prodding to awaken interest in the problem. In 
the popular education on health matters the medical profession should 
lead, especially through the health authorities. This has also become 
one of the manifest duties of the practitioner. 

Cleanliness. — After all, the prevention of hookworm disease is a 
question of decency and cleanliness. Water sometimes carries the in- 
fection, hence it should be clean or cleansed by filtration or boiling. 
Soiled hands may carry the infection to the mouth, hence they should 
be washed before eating. Vegetables fertilized with night soil may be 
infected. This practice is not clean and should be forbidden, especially 
in the case of those vegetables usually eaten raw. With cleanly habits 
there would be no soil pollution, and the disease would be checked. 

Personal Prophylaxis. — Personal prophylaxis consists in wearing 
shoes and otherwise avoiding contact with the infected soil. Brick 
makers, miners, and others compelled to work in infected soil should 
wear gloves. Other measures, such as boiling the water, eating only 
cooked or clean food, washing the hands, and avoiding the infected area. 


have either been dwelt upon or are too obvious to need further em- 

Immigratiox. — An important factor in the spread of hookworm 
disease in the United States is immigration. Every country that brings 
laborers from infected regions is bringing in a constant stream of infec- 
tion. California has established quarantine measures against Indian 
coolies, 90 per cent, of whom are infected. 

Collateral Benefits. — The best part of a hookworm campaign is 
the collateral good it does. This applies as well to a sanitary campaign 
directed against almost any disease. The suppression of hookworm 
disease will diminish the amount of tuberculosis, typhoid fever, dysen- 
tery, and other infections. Thus, in Bilibid prison, Manila, the death 
rate was formerly excessive — 234 per thousand when the Americans 
took charge. This Avas reduced to 75 per thousand by sanitary 
measures, such as boiled water, screens, disinfection, improved food, 
less crowding, better air, more sunlight, etc., but despite these sani- 
tary improvements the death rate could not be hammered doAvn below 
75 per thousand. Then it was found that many of the prisoners were 
infected with hookworms. Thymol was administered and the death 
rate fell to 13.5 per thousand. Another instance of the collateral bene- 
fits resulting from sanitary work is the plague campaign in San Fran- 
cisco, which cut typhoid fever in half, although no special attention 
whatever was paid to the latter disease. The purification of the water 
supply in Hamburg by filtration cut down the general death rate and 
diminished the morbidity of diseases not water-borne. One of the most 
encouraging phases of sanitary work directed against tuberculosis, ty- 
phoid fever, and hookworm disease is the assurance that a successful 
campaign will result in fundamental and permanent control or eradi- 
cation of other communicable diseases. The prevention of tuberculosis 
deals especially with personal hygiene, and the prevention of typhoid 
fever and hookworm with the sanitation of the environment. The com- 
bination of the two, therefore, embraces almost the entire range of pre- 
ventive medicine. 




Tuberculosis is the most frequent and widespread of all the major 
infections. In this country 9 per cent, of all deaths, and in Germany 
12 per cent., are caused by tuberculosis. The toll falls heaviest dur- 
ing the period of life of greatest usefulness — thus 30 per cent, of all 
deaths between the years of 15 and 60 are due to pulmonary tuber- 
culosis alone. Xaegeli, from a careful examination of a large number 
of bodies in Zurich, found evidence of tuberculosis in over 90 per cent. 
The lowest figures based on the evidence of pathologic anatomy are 
those of Bitzke, who examined 1,100 bodies in Berlin. In children 
under 15 he found evidence in 27.3 per cent., and in persons over 15 
58.2 per cent. The difference between Naegeli's figures and Bitzke's 
is due to a difference in the interpretation of the pulmonary scars 
and adhesions at the apices, and the small fibrous nodules in the 
lungs. Bitzke does not consider such lesions as of tuberculous origin, 
and leaves them out of his figures. If these were included, his 
percentage would also be very much higher. The frequency with 
which we become tuberculized is indicated by the fact that practically 
all persons more than a few years old give the von Pirquet cutaneous 

In the United States it is estimated that 160,000 persons die each 
year of tuberculosis. Of the 90.000,000 people now living in this 
country, it is estimated that 8,000,000 are doomed to die of tuber- 
culosis, unless the disease is checked. The loss in life and treasure is 
appalling. It is, therefore, most encouraging that preventive measures 
based upon modern conceptions of the disease as a communicable in- 
fection are giving encouraging results. 

Tuberculosis began to decline before the nature of the infec- 
tion was known. The decline is gradual. Modern methods have 
so far made little apparent impression upon the gross amount 
of the infection. The social and economic conditions of the 


mass of the population must be improved before any great decline 
in the mortality rate can be expected, as will presently be pointed 

Tuberculosis is fast becoming, in fact already is, a class disease; 
it is much more prevalent among the poor than the well-to-do. Hence 
the prevention of tuberculosis has become a sociological problem. Pov- 
erty with all its attendant hardships, such as poor food, bad housing, 
overwork, and worry, diminishes resistance to the infection; while pros- 
perity, which buys good food, rest, change of air and scene, choice of 
occupation, and diversion, increases our resistance to the infection. 
An increase of wage or decrease in the cost of living; shortening the 
hours of work; improving the conditions of industrial hygiene; adding 
to the number of holidays; playgrounds, parks, and wholesome recrea- 
tion, all help to increase our resistance against and diminish the 
prevalence of tuberculosis. Science has shown the way; it remains 
for society to apply the knowledge. 

The Difference Between the Human and the Bovine Tuhercle Bacilli. 
— There are at least three kinds of tubercle bacilli : human, bovine, and 
avian. The human and bovine varieties resemble each other closely; 
the essential difference lies in the fact that the human type is very 
pathogenic for man, but has little pathogenicity for cattle, rabbits, 
guinea-pigs, monkeys, and other animals. On the other hand, the 
bovine type is very pathogenic for almost all mammalian animals ex- 
cept man; it is pathogenic for man, but less so than the human bacil- 
lus. Even when large numbers of the human variety are injected 
into a calf, a general disease does not usually result; at most only a 
local lesion is produced. One one-hundredth of a gram of a pure cul- 
ture of a bovine race injected subcutaneously is sufficient to cause 
generalized tuberculosis and death in a rabbit in about 6 weeks; while 
ten or a hundred times this quantity of a human strain produces at 
most a slight localized tuberculosis. 

The human bacillus grows more luxuriantly upon culture media, 
covering the entire surface of the medium with a rich, dry, crinkled, 
mold-like vegetation. The growth of the bovine bacillus upon artificial 
culture media is more sparse, thinner, less extensive, and somewhat 
slower. According to Theobald Smith, who first pointed out the differ- 
ences between these two types, the human bacillus produces more acid 
in artificial culture media and a different reaction curve than that pro- 
duced by the bovine bacillus. 

Morphologically the bovine bacillus is usually shorter, plumper, and 
stains more uniformly than the human bacillus, which is ordinarily 
club-shaped, irregular, and stains with interrupted markings. The 
morphological and tinctorial characters are not sufficiently distinctive 
to distinguish one type from the other. 


It is doubtful \vheth(ir there are any specific differences between 
the tuberculins of bovine and lunnan origin. 

The avian tubercle harillu.s is found most frequently in chickens 
and also in pigeons, pheasants, and guinea-fowl. Geese and ducks ap- 
pear immune. The avian bacillus is quite pleomorpliic and stains some- 
what more readily tlian either the human or bovine types. The avian 
bacillus grows luxuriantly upon artificial culture media at 45° C. and 
even multiplies at temperatures as high as 50° C, which is in marked 
contrast to the mammalian types, which do not vegetate above 40° C. 
The avian bacillus grows rapidly, so that upon glycerin-agar or upon 
blood serum there is an abundant growth in 10 days, which consists 
of a white, moist, and fatty mass quite different in young cultures from 
the dried and crinkled appearance of the human type. Guinea-pigs 
show a decided resistance to the avian cultures, but rabbits are suscep- 
tible. Chickens and pigeons may be infected with certainty by feeding, 
and it is probable that in nature avian tuberculosis is generally trans- 
mitted in this way. 

Fish tuberculosis shows a marked difference to the races found in 
warm-blooded animals. The bacillus grows between 12° and 36° C, 
the optimum temperature being 25° C. It was first found in a carp 
and is pathogenic for frogs. Neither the avian nor the fish tubercle 
bacilli are pathogenic for man. 

Bovine Tuberculosis in Man. — Concerning bovine tuberculosis in 
man we now possess definite knowledge which permits of precise state- 
ments. At one time the danger of bovine tuberculosis to man was 
greatly exaggerated. Koch went too far on the other side when he 
announced at London before the International Congress on Tuberculosis 
in 1901 that there was practically no danger of man contracting tuber- 
culosis from cattle. In recent years Koch modified this dictum, for it 
was soon proven that the bovine bacillus has a certain amount of patho- 
genic power for man and that some of the tuberculosis in man is con- 
tracted from bovine sources. If only 1 per cent, of the deaths from 
tuberculosis in the United States were caused by bovine tubercle bacilli, 
it would mean 1,600 deaths yearly. It is now estimated that perhaps 7 
per cent, of the tuberculosis in man is of bovine origin. 

Pulmonary tuberculosis in man is practically never associated with 
the bovine bacillus. Bovine tuberculosis in man is usually a disease 
of the lymph glands — the l}Tnph nodes of the cervical region and the 
lymph nodes in the abdomen being especially attacked. This is doubt- 
less due to the fact that the portal of entry of the bovine bacillus is 
usually through the tonsils or the small intestines. Bovine tubercu- 
losis may become a fatal infection in man when it is generalized through 
the blood in the form of acute miliary tuberculosis or when it localizes 
in the meninges or other vital parts. About one-quarter to one-half 



of all cases of tuberculosis in children under 5 years of age is associated 
with the bovine type. It is probable that all these cases derive their 
infection through the tubercle bacilli in cow's milk. There is 
little danger from meat, as this is usually cooked, and tubercu- 
losis of the muscles is exceedingly rare. Meat may become con- 
taminated with tubercle bacilli as a result of unclean butcher's 
tools or unsanitary methods of handling, or from tuberculosis of 
attached glands. 

The following table shows the relation between bovine and human 
tuberculosis in 1,040 cases. Six hundred and six of these cases were 
collected from the literature and include those studied by the English 
and German Commissions; 434 of the cases were studied in the re- 
search laboratory of the New York Board of Health by Park and 
Krumwiede : 


Diagnosis of Cases Examined. 

16 Years 
and Over. 

5 Years to 
16 Years. 


5 Years. 








Pulmonary tuberculosis 



Tuberculous adenitis, inguinal and axil- 



Tuberculous adenitis, cervical 






Abdominal tuberculosis 





Generalized tuberculosis, alimentary 



Generalized tuberculosis 





Generalized tuberculosis including men- 



Tubercular meningitis 




Tuberculosis of bones and joints 




Genitourinary tuberculosis 




Tuberculous abscesses 









Total Cases, 426. 



Diagnosis of Cases Examined. 

16 Years 
and Over. 

5 Years to 
16 Years. 


5 Years. 







Pulmonary tuberculosis 





Tuberculous adenitis, axillary 



Tuberculous adenitis, cervical 







Abdominal tuberculosis 







Generalized tuberculosis, alimentary 







Generalized tuberculosis.. 






Generalized tuberculosis including men- 
inges alimentary origin 





Generalized tuberculosis including men- 




Tubercular meningitis 



Tuberculosis of bones and joints 






Genitourinary tuberculosis 


Tuberculosis of skin 




Miscellaneous Cases: 

Tuberculous tonsils 




Tuberculosis of mouth and cervical 

Tuberculous sinus 

Sepis latent bacilli 








Mixed or Double Infections, 3 

Generalized tuberculosis. Alim. Orig. 30 yrs. Human and bovine type in 

mesenteric node. Human type in bronchial node. 
Generalized tuberculosis. Alim. Orig. 5^ yrs. Human type in spleen. 

Bovine type in mesenteric node. 
Generalized tuberculosis incl. meninges. Alim. Orig. 4 yrs. Human type in 
meninges and bronchial nodes. Bovine type in mesenteric nodes. 

Total Cases, 606. 

From a study of these 1,040 cases we find : 

16 years and over 686 cases — 9 with bovine bacilli — 1.3% 

Between 5 and 16 years 132 " —33 " " " —25.0% 

Under 5 years...." 120 " —59 " " " — 19.1% 

Of 568 cases of pulmonary tuberculosis, none had the bovine bacil- 
lus. Cases under 5 years of age, 15 per cent. 



It should be remembered that many of the cases included in the 
above total were selected cases. The 436 cases studied in the Eesearch 
Laboratory in New York, however, were not selected; of these cases 
the following were found associated with the bovine bacillus: 



Five to 


Pulmonary tuberculosis 

Tuberculous adenitis, cervical 

Abdominal tuberculosis 

Generalized tuberculosis 

Tubercular meningitis with or without generahzed 


Tuberculosis of bones and joints 








Since the above tabulations Park and Krumwiede ^ have collected a 
total of 1,511 cases which give the following: 



Adults 16 

Years and 


5 to 16 


Under 5 

Pulmonary tuberculosis 

Tuberculous adenitis, cervical 

Abdominal tuberculosis 

Generahzed tuberculosis, ahmentary origin .... 

Generahzed tuberculosis 

Generahzed tuberculosis, including meninges, 
ahmentary origin 

Tubercular meningitis (with or without general- 
ized lesions other than preceding) 

Tuberculosis of bones and joints 

Tuberculosis of skin 















As is evident from the table summarizing the total cases reported, 
many of those in children had slight or latent infections, found on their 
death from other causes. The percentages deduced, therefore, only give 
the incidence of infection, nothing more. 

Weber, of the Imperial Board of Health of Germany, has made 
observations to determine just how much danger there is in drinking 
milk containing bovine tubercle bacilli. The milk coming from all 
known cases of udder tuberculosis was traced to the consumer and all 
the persons drinking such milk or using fresh milk products from in- 

Wour. Med. Research, XXVII, 1, Sept., 1912, 


fected sources were examined with reference to tuberculosis. In all 
113 separate investigations were made, including 628 persons (284 of 
whom were children, 335 were adults, and 9 of unstated age), all of 
whom had undoubted opportunities of consuming milk or fresh milk 
products from cows having tuberculosis of the udder. The evidence 
presented is not equally valuable in each investigation. In 44 of the 
113 investigations cited, the milk was either heated, used in coffee or 
tea, or mixed with milk from apparently tuberculosis-free cows before 
it was consumed. 

Three hundred and sixty persons (of whom 151 were children, 200 
adults, and 9 of unknown age) were known to use milk or milk prod- 
ucts, such as butter, buttermilk, sour milk, and cheese, which came 
from cows having undoubted tuberculosis of the udder. Of these 360 
persons 2 were shown, by actual animal experimentation, to have in- 
fections with the bovine tubercle bacillus. Both positive cases were 
children with tuberculous neck glands. Six other children and 1 adult 
had glandular swellings in the neck, and in 4 other children and 1 
adult there was a strong suspicion on the part of the attending physi- 
cian that abdominal tuberculosis was present. 

In another series of 360 persons, 12 children and 1 adult had swell- 
ings of the lymph glands of the neck. In this group the diagnosis was 
not confirmed bacteriologically. 

Weber concludes from these studies that the danger which man un- 
dergoes through the consumption of uncooked milk and milk products 
of cows having tuberculosis of the udder is similar to the danger which 
persons having well-marked pulmonary tuberculosis exhibit for their 
fellowmen, although very much less. He believes it is fair to assume 
from the statistics presented above that the danger from drinking un- 
cooked milk or using milk products of cows with tuberculous udders is 
surprisingly small. 

Woodward voices the prevailing opinion when he maintains that the 
more deeply we go into the subject, the bovine side of the question comes 
to take a larger and larger place, especially in connection with surgical 
and abdominal tuberculosis, not only in the child but even in the 

From the standpoint of our present knowledge we must consider 
that practically every case of bovine tuberculosis in man is ingestion 
tuberculosis, contracted from milk or fresh milk products. How the 
tubercle bacilli get into milk and the frequency with which it is in- 
fected are discussed on page 513. 

Occasionally butchers and also pathologists at autopsies become in- 
fected with the bovine bacillus through wounds. These accidents fur- 
nish further experimental proof that the bovine type of the tubercle 
bacillus possesses a certain degree of pathogenicity for man. 



There are two great sources of human tuberculosis: the principal 
source is man himself; the secondary source is cattle. 

From man tubercle bacilli leave the body mainly in the sputum, 
where they are found in great numbers in all open cases of pulmonary 
tuberculosis. Tubercle bacilli may also leave the body in the discharges 
from any open tuberculous lesion wherever situated, especially in dis- 
charges from the lymphatic glands, bones, intestinal or genitourinary 
tracts, or the skin. In pulmonary tuberculosis some of the sputum is 
swallowed and the bacilli appear in the feces, therefore any or all of 
the discharges from the body may be infective. But, from the prac- 
tical standpoint of prevention, the bacilli in the matter brought up 
from the lungs is the source of the danger in the overwhelming ma- 
jority of cases. 

Practically all observers agree with Koch that human sputum is 
the main source of human tuberculosis. Whether the tubercle bacillus 
is usually transferred directly or indirectly, in moist or in dry state, 
by inhalation or ingestion, are questions still undetermined. The ques- 
tion at issue is a quantitative one; that is, how often are we infected 
by the direct aerogenic route, how often through the tonsils and upper 
respiratory passages, how often through the digestive tube, etc. ? 

Aerogenic Infection.' — The belief that tuberculosis is air-borne, that 
is, that pulmonary tuberculosis is a primary inhalation tuberculosis, 
has long been the natural and favorite theory, from the fact that the 
lungs are most frequently affected. This opinion was strongly ex- 
pressed by Koch in 1884, and repeated by him in 1901, at the British 
Congress on Tuberculosis. For many years it found practically uni- 
versal acceptance. Cornet taught that the tubercle bacilli entered the 
lungs in the dust of dried and pulverized sputum. 

The evidence of pathologic anatomy strengthens the belief in the 
importance of aerogenic infections as the chief portal of entry. Thus, 
the recent studies by Ghon,^ at the St. Anne's Children's Hospital in 
Vienna, indicate very strongly that the actual path of infection is by 
the aerogenic route. Approximately 95 per cent, of 184 autopsies studied 
by him represent a primary localization of the bacilli in the lungs. On 
the other hand, it seems that direct aerogenic infection has been greatly 
overestimated, and some students of the subject go so far as to state 
it is of little or no practical importance. It is supposed that very few 
bacteria suspended in the air actually reach the lungs, being caught 
on the moist mucous membranes of the upper air passages. Fur- 
ther, tuberculosis of the lungs is usually at the apex, which is not 
in the direct line that floating particles in the air would usually be 
^"Der primare Lungenherd bei der Tuberkulose der Kinder," Berlin, 1912. 


meclianically carried. It is true that dust under certain conditions 
may contain tubercle bacilli, but it is now known (hat this organism 
soon dies when exposed to tlic sun and air, and that the dust out of 
doors is not a])t to contain the live bacilli, and when it does so the 
dilution must be enormous. It is difTerent witli liouse dust. Tul)ercle 
bacilli may live a long time in dark, moist })laces, but even here the 
danger cannot be as great as might be supj)Osed when we study the na- 
ture of tulx-rculous sputum. This substance is usually tenacious and 
gummy, and dries into tough, glue-like masses, which are pulverized 
with great ditRculty. It therefore seems imlikely that dust under ordi- 
nary circumstances wouhl contain dangerous numbers of live tubercle 
bacilli. 'J'lie danger from this source is further diminished when we 
consider that a large nuinl)er of tubercle bacilli die in sputum even 
when protected from sunlight and other injurious influences. It is 
now known that even under most favorable conditions in artificial cul- 
ture media the great majority, perhaps 99 per cent., of the bacilli die 
within three months. Transplants made from cultures over three months 
old usually do not grow. The danger of house dust containing live 
tubercle bacilli from a quantitative standpoint is, therefore, reduced. 

It is quite possible that the first infection does not produce the dis- 
ease; that is, when a few tubercle bacilli land upon the lungs the tis- 
sues do not react and the bacilli are carried to the bronchial lymph 
glands. This first infection, however, sensitizes the parts, so that the 
second time the bacilli lodge the tissues react vigorously and a local le- 
sion may result. A dusty atmosphere, even though it contains no tu- 
bercle bacilli, is, however, exceedingly dangerous, in that it irritates the 
delicate mucous membranes and thus opens the door for infection. 

One point of importance in this controversy is the experimental 
evidence that it requires very few tubercle bacilli by inhalation to pro- 
duce the disease, whereas it requires hundreds and even thousands to 
cause intestinal infection. This is given as a reason why infection via 
the digestive tract is comparatively rare in man, for he fortunately 
would seldom receive the necessary numbers of human bacilli by the 

Cornet and others have actually found live tubercle bacilli in the 
dust and upon objects of rooms where tuberculous patients are care- 
less with their sputum. In one of Cornet's experiments 47 out of 48 
guinea-pigs exposed to the dust produced by sweeping a carpet with a 
stiff broom became tuberculous. The carpet had been purposely in- 
fected with tuberculous sputum shortly before. Dust containing tu- 
bercle bacilli may also enter the atmosphere from soiled linen, uphol- 
stery, handkerchiefs, and other fabrics containing the dried tuberculous 
sputum. Tuberculous dust may also be stirred up by walking over 
floors and the dragging of the infection by ladies' skirts. 


Droplet Infection. — When it was found that the danger from dust 
theoretically was not as great as was supposed, Fliigge called attention 
to the fact that in speaking, coughing, sneezing, and in other violent 
expiratory efforts the fluid contents of the mouth are sprayed into the 
air in the form of a fine mist. These tiny droplets contain tubercle 
bacilli or germs of any other infection that may be in the mouth. Or- 
dinarily these droplets are carried several feet, but under exceptional 
circumstances may be carried 30 or 40 feet or more; however, at these 
distances the dilution is enormous and the danger, therefore, much 
diminished. The tubercle bacilli contained in the droplets sprayed from 
the mouth are fresh and virulent, and may land directly upon the 
mucous membranes of the healthy individual or may be conveyed in- 
directly through food, fingers, and other objects. There is danger from 
droplet infection, but it cannot be the usual mode of transmission in 
tuberculosis from the nature of the circumstances. The danger from 
droplet infection is increased by close association with the patient in 
stuffy, ill-ventilated rooms, especially if the individual docs not take 
proper care in coughing and sneezing. For a further discussion of 
droplet infection see page 632. 

Ingestion Infection. — Little by little the view gained ground that 
some cases of tuberculosis, particularly in children, might be due to 
bacilli entering through the mucous membrane of the alimentary canal. 
Now we recognize that much of the tuberculosis in children comes through 
the alimentary tract. Many years before the discovery of the tubercle 
bacillus Chauveau (1868) Avas inclined to the belief that the alimentary 
canal may be the portal of entry in tuberculosis. Woodward in 1894 
maintained that the infecting bacilli might reach the lungs through 
some part of the alimentary canal. He drew attention to the fact that 
in many children, and also in animals fed on tuberculous material, the 
lungs may be markedly affected. He traced the course of the infection 
through caseous or old calcareous mesenteric glands up through the 
diaphragm to the posterior mediastinal glands, and so to the lungs. 
Still in 1899 analyzed 259 fatal cases of tuberculosis occurring in the 
Hospital for Sick Children, London, and concluded that the infection 
had occurred through the alimentary canal in 20.5 per cent, of the 
cases. Shennan in 1900, dealing with 316 autopsies at the Eoyal Hos- 
pital for Sick Children in Edinburgh, found this ratio to be 28.1 ner 

There is no doubt that the lungs are more or less involved in all 
cases of generalized infection, especially in children, but these are not 
cases of pulmonary tuberculosis (phthisis) in the usual meaning of the 
term. It is phthisis or pulmonary tuberculosis which causes 70 per 
cent, of all the mortality from tuberculosis and whose mode of origin 
is now in question. 


Behring in 1903 maintained that the tubercle bacilli might be taken 
up from the intestine and pass through the mesenteric glands, so gain- 
ing access by the blood stream to the lungs without leaving any le- 
sion in the gut or glands to mark the portal through which they had 
entered or the route by which they had traveled, and that pulmonary 
tuberculosis was commonly caused in this way. Behring's theory of 
the origin of phthisis did not find a ready acceptance. Nevertheless, 
the belief that phthisis may be caused by bacilli which have been swal- 
lowed and absorbed from the digestive tube gradually gained ground. 
Vallee in 1904 concluded from his own investigations that ingestion 
of dust or food infected with tubercle hacilli was the quickest and 
surest method of infection. A little later Calmette (1905) of Lille 
appeared as a strong supporter of this view. Calmette went so far as 
to assert that the immense majority of cases of pulmonary tul)ercul()sis 
in man are caused by ingested bacilli and not by inhalation. Whitla, 
in 1908, and Symmers repeated some of this work and became con- 
verted to Calmette's doctrine, and these views have gained a number 
of adherents. Cobbett (1910) considers that the ingestion theory is 
based on a slender substructure of experiments from which too sweep- 
ing conclusions have been found. Thus Calmette and his colleagues 
claim that even anthracosis is caused not by the carbon particles in- 
haled, but the particles ingested, which pass through the intestinal 
mucosa and lodge in the lungs. Cobbett showed the experimental error 
and demonstrated that India ink intimately mixed with cream is not 
absorbed in any great amount from the intestine, for the cream reap- 
pears of a normal color in the lacteals. He found, however, that feed- 
ing finely divided carbon matter caused traces of pigmentation in the 
lung and bronchial glands when long continued. Heller and Vulcan- 
stein showed that the feeding of large amounts of coal dust never pro- 
duces that grade of anthracosis which is found after the inhalation of 
much smaller amounts. 

There is now sufficient proof to state definitely that tubercle bacilli, 
when taken in food or drink, may pierce the mucous membrane of the 
digestive tube and produce lesions in distant parts of the body. It is 
also demonstrated that the tubercle bacillus may thus travel without leav- 
ing macroscopic evidence of its passage in its wake. Fraenkel ^ and 
others have shown that the tubercle bacilli may jjass through the un- 
injured skin of guinea-pigs, leaving no trace of their passage at the 
place where they had rubbed upon the skin, but causing tuberculosis 
of the internal organs. Ravenel and others have shown that tubercle 
bacilli may pass through the intestinal wall without leaving a trail be- 
hind them. It does not, therefore, necessarily follow that the seat of 

'^Hyg. Bundschau, XX, 15, Aug. 1, 1910, p. 817. 


the primary lesion in tuberculosis is the site of the entrance of the in- 

It is also claimed that, no matter how the tubercle bacillus reaches 
us, whether in dust or droplets, by kissing or through fingers, flies, 
cups, handkerchiefs,' or milk, it either passes through the tonsils or 
mucous membrane of the ujjper respiratory passages, or is carried into 
the intestinal tract and absorbed from the intestines. A^iewed in this 
light, the portal of entry even in dust infection may be through inges- 
tion rather than through direct aerogenic infection of tbe lungs. Ex- 
perimentally it is easy to prove that tubercle bacilli given by the mouth 
may produce a generalized and fatal tuberculosis; thus, of 100 guinea- 
pigs given one large feeding of a bovine culture by Eosenau and An- 
derson, 99 died of tuberculosis. That infection by ingestion does 
not tell the whole story is judged from the fact that primary tu- 
berculosis of the mesenteric nodes in man is not as common as we 
might expect. On the other hand, it is claimed that the tubercle bacil- 
lus may pass these lymph glands, leaving little or no trace behind them. 
Thus the work of Weichselbaum and his pupils, Bartel, Xeuman, and 
Spieler, strengthens the importance of ingestion as the portal of entry. 
These investigators found that the tubercle bacillus produces, in addi- 
tion to the specific tubercles, other lesions of a simple lymphatic hyper- 
plastic character. These earty lesions are called the ''lymphoid stage" 
("hTQphoide stadium"). The recognition of this early stage is of 
importance in determining the point of invasion. The evidence ob- 
tained from the macroscopic appearance of the lesions at autopsy must 
be supplemented by microscopic studies. Bartel and Spieler found that 
in ingestion experiments the different lymphatic groups were infected 
with the following frequency, judged by the hmphoid stage: 

Tonsils and surrounding. .. .11.7 per cent. 

Cervical glands 58.8 per cent. 

Bronchial glands 52.9 per cent. 

Mesenteric glands 100.0 per cent. 

These investigators assume that the tubercle bacillus is carried from 
the mesenteric or the neck glands either through the lymphatics di- 
rectly or through the thoracic duct and the arterial circulation to the 
lungs and other tissues and organs of the body. The disease usually 
localizes itself in the lung because this organ presents the least re- 

"Weichselbaum believes that ingestion tuberculosis occurs much more 

often in man than is commonly supposed and especially in children. He 

assumes that the tubercle bacilli may pass through the mouth, nose, or 

throat. It seems immaterial whether the bacillus is taken with food 


or other substances placed in the mouth, or is contained in the inspired 
air, or enters the mouth and nose through any other medium. The 
first lesions do not consist in the formation of specific tubercles, but in 
the so-called lymphatic tuberculosis. This stage lasts a variable time 
and may end in recovery or may lead to specific tuberculosis either 
through reinfection, or it may light up itself without a new infection. 
The specific tubercles may occur cither at the portal of entry or in the 
lungs and bronchial glands or in other organs. 

Bchring (1903) brought forward the theory that alimentary infec- 
tion occurs in the early months of life. The tender mucous membrane 
of babies permits the bacillus to pass readily. The bacilli remain latent 
in the tissues and acquire increased activity later in life. According to 
this view tuberculosis of adults is the "end of a song, the beginning of 
which for the unfortunate patient was sung in the cradle.'' If this 
view were correct, the majority of cases of tuberculosis in adults would 
be associated with the bovine bacillus, unless the bovine bacillus has the 
power of changing to the human type during its long stay in the body. 
This is not likely. 

It is clear from the evidence at hand that ])ulmonary tul)erculosis 
may arise either by inhalation or by ingestion. The problem for \\s now 
to solve is a quantitative one; that is, what percentage of eases are 
air-borne and what percentage come through the mucosa of the digestive 
tract? Opinions differ widely, but opinions are of little value. We 
must have the facts before we can give the final answer to this very 
important and practical question.^ 

Flies. — Under certain circumstances flies may readily transfer tu- 
bercle bacilli from exposed sputum to fingers, lips, or food. This may 
account for an occasional case. 

Water. — Large quantities of tuberculous sputum that escape dis- 
infection and an additional large number of tubercle bacilli in the ex- 
creta finally reach the drinking water. The tubercle bacillus is particu- 
larly resistant to putrefactive processes, and may live a long time in 
water. The use of contaminated water can, therefore, not be disre- 
garded. A study of the vital statistics of Hamburg, Lowell, and Law- 
rence seems to show a diminution in tuberculosis following a purification 
of the water supply by filtration (Mills-Iieinke Phenomenon, page 804). 

Contact Infection. —The majority of cases of tuberculosis contract 
the disease through "contact." Contact infection is a general and con- 
venient term ; it implies the rather quick transference of fresh infec- 
tion in which the bacilli pass from one individual to the other in a 
brief space of time and through a short distance. Contact infection 

^ An exhaustive and able summary of this question will be found in Bulloch's 
article in Allbutt 's ' ' System of Medicine, ' ' from which some of the facts in 
this article have been used. 


may be either direct or indirect; through dust^ through bacilli in the 
air, or through contaminated food, through soiled fingers or objects; 
through flies, as well as in numerous other ways. The infections trans- 
ferred through kissing, pencils, pipes, toys, cups, and other objects all 
come under the convenient category of "contacts." Even the infection 
through droplets is included in the present-day conception of contact 
infection. The term is a practical one, and implies close association, 
though not necessarily actual contact, between the sick and the well. 
Viewed in this sense, tuberculosis is a house disease or a family disease. 
With this conception it makes little practical difference whether the 
infection enters the body through the respiratory tract or the digestive 
tube. Either or both would be possible in regarding the disease as con- 
tagious in the sense of contact infection. 

Although there is some doubt concerning the exact mode of trans- 
mission and the portal of entry that the tubercle bacillus usually takes, 
we have sufficient knowledge to guide our preventive measures with 
every assurance of success. One thing is certain : tuberculosis is an 
infection spread mainly from man to man, usually through direct as- 
sociation between the sick and the well; and secondarily from cows, 
through milk, 


Man possesses a considerable resistance to tuberculosis. This is 
shown by the fact that many cases recover spontaneously and that per- 
haps all individuals who reach the age of 30 years and who spend most 
of this time in association with their fellowmen under the usual urban 
conditions have at one or more times been infected. The resistance to 
tuberculosis increases after middle life, due perhaps to the immunity 
which is induced by these prior infections. There is probably no true 
racial immunity to tuberculosis. Some races show a smaller incidence 
to the disease, owing probably to modes of life, habits of nutrition, and 
conditions of exposure. 

The human organism is capable of taking care of a certain amount 
of infection. The dose, that is, the number, of tubercle bacilli and 
their virulence, is, therefore, a very important factor in determining in- 
fection. This may readily be demonstrated upon susceptible animals 
and is doubtless true of man. Frequent reinfections occurring at short 
intervals with small numbers of tubercle bacilli doubtless break down 
the immunity. In man the balance between immunity and susceptibility 
to tuberculosis is delicately adjusted : there is a very small factor of 
safety. The resistance to the infection may be increased by attention 
to personal hygiene, fresh air, and good food; immunity may readily 
be broken down by any weakening influence; herein lies the keynote of 
personal prophylaxis. 


Tlie immunity to tuberculosis is not sufficiently strong to overcome 
a large amount of infection. As in all other infectious j)rocess-es, the 
strongest and most robust individuals in the jiriine of life succumb to 
the disease in a short time if they receive into their system a large 
number of virulent tubercle bacilli. Hence the avoidance of the in- 
fection is one of the most important of our preventive measures. 

The mechanism of the immunity to tuberculosis is ])robably exceed- 
ingly complex. There is no antitoxic immunity. The tuberculins are 
not true toxins. Phagocytosis and cellular reactions play a very im- 
portant role. The recent studies upon anaphylaxis throw a certain 
amount of light upon the mechanism of immunity in tuberculosis. The 
phenomenon of hypersusceptibility is beautifully illustrated in the action 
of tuberculin, which is a comparatively harmless substance to a normal 
individual, but produces a marked reaction in a sensitized individual. 
This reaction must be useful in protecting the organism against the 
invasion of the tubercle bacillus, and also in guarding it against the 
spread of the disease after it has become localized. Thus, if tuberculin 
is placed upon a normal conjunctiva no reaction follows.^ This first 
application, however, sensitizes the tissues of the conjunctiva so that, 
if the application is repeated after the lapse of a few weeks, there is a 
violent reaction. The same phenomenon doubtless occurs when a tubercle 
bacillus lodges in a lymph gland or in the lung or some other part of the 
bod}'. The first time it meets with little resistance; the next time the 
tissues react immediately and vigorously. All of nature's protecting 
agencies, such as the germicidal substances in the blood, the phagocytic 
cells, and antibodies, are concentrated upon the point where they are 
most needed. In the same way the body protects itself against the ex- 
tension of a tuberculous focus. The parts surrounding a tubercle become 
sensitized and react so as to encapsulate the focus with a cellular and 
fibrous coat of mail. This reaction is probably stimulated by small 
amounts of tuberculin produced within the tuberculous focus. ^Yhen 
the tuberculin is not produced autogenously in sufficient amounts, as in 
chronic lesions of the bones, or inactive processes of the glands or skin, 
the specific reaction may be stimulated to advantage by the injection of 
small quantities of tuberculin. If, however, the tuberculin is given in 
too large amounts or too frequently, the power of reaction is readily 
broken down. When this occurs the mechanism of immunity has been 
destroyed, there is little resistance left to the extension of the infection, 
and death soon occurs. Clinical experience has demonstrated the danger 
of large doses of tidjerculin or small amounts too often repeated in tuber- 
culosis. The same may readily be demonstrated experimentally in the 
lower animals. These facts are of fundamental importance in the use 
of tuberculin. 

' Eosenau and Anderson, J. A. M. A., Vol. I, March 28, 1908, p. 961, 


It is quite proper to deny dogmatically the hereditary transmission of 
tuberculosis in educational pamphlets for popular use. The infection 
is not transmitted hereditarily, although it occasionally passes from 
mother to fetus congenitally. Tubercle bacilli do not occur in the sper- 
matozoon, and do not appear in the seminal fluid. They are not found 
in the ovum; in fact, a tubercle bacillus in the ovum would doubtless 
result in the death of the egg. The bacilli, however, may pass from 
mother to fetus through the placenta. Warthin shows that placental 
tuberculosis is more common than is supposed. The lesions in the 
placenta are not those of t3qoical tubercle formation. 

While the tubercle bacillus itself is rarely transmitted from parent 
to offspring, an hereditary tendency or disposition to the disease may 
be transmitted. We have no definite knowledge as to what this de- 
creased resistance consists in; it may be a diminished power of reac- 
tion. For this view there is analogy in the experiments upon anaphy- 
laxis in guinea-pigs, in which it has been shown that hypersusceptibility 
to a foreign protein such as tuberculin may be transmitted from mother 
to young. 

A mild infection with bovine tuberculosis in early life seems to 
leave a certain degree of immunity against the human strain. At least 
children who have glandular tuberculosis of the bovine type in child- 
hood are said to be less apt to have tuberculosis of the lungs in later 
life. Likewise, the human strain injected into cattle produces a defi- 
nite immunity against the bovine type. Cattle are now immunized 
by the intravenous injection of 2 c. c. of a suspension of a pure cul- 
ture of the human tubercle bacillus. This produces an immunity which 
probably lasts for 1 to 2 years. It should be remembered that the hu- 
man bacillus under these circumstances remains alive for a very long 
time, and may appear in the milk provided there is a lesion in the 
udder. This presents a danger which cannot be disregarded. 

Trudeau long ago showed that the only definite immunity that could 
be induced in experimental animals was through the use of live tubercle 
bacilli. Webb and Williams ^ have produced a certain amount of im- 
munity in guinea-pigs and monkeys by the injection of live tubercle 
bacilli. The first injection consists of the introduction of a few bacilli 
(from 1-200), which is repeated subcutaneously at varying intervals. 
Two children have also been successfully "vaccinated" with upward of 
600 virulent human tubercle bacilli without infection being produced. 


We have no easy method of determining just when the tubercle bacil- 
lus dies. The criterion of death depends upon animal experimentation. 

^"Immunity in Tuberculosis," J. A. M, A., Oct. 28, 1911, Vol. LVII, 
No. 18, p. 1431. 


Tlie tubercle bacillus has no spore and may be classed with other non- 
spore-bearing organisms so far as its viability is concerned. Its virulence 
fades before it dies. It is doubtful whether the waxy substances protect 
the bacillus against external harmful influences to any unusual extent. 
The thermal death point is 60° C. for 20 minutes. This is much less 
than was once considered.^ Failure to recognize the lesions produced by 
the dead tubercle bacillus is responsible for some of the false conclusions 
reached by experimenters upon this sul)ject. 

From a practical standpoint the resistance of the tubercle bacillus 
in sputum is of prime importance. Protected from the sunlight it is 
now known that they may live in dried sputum for months. All tlie 
bacilli do not survive under these conditions, but we lack methods to 
determine the quantitative reduction. 

The tubercle bacillus withstands cold very well. It has a marked 
resistance against putrefactive processes. It will live a year in water, 
which is a fact not to be neglected, as many tubercle bacilli finally find 
their way into drinking w'ater, and infection through this source is 

For the destruction of the bacilli in sputum only very strong 
germicides or exposure to steam or boiling water should be depended 
upon. Five per cent, carbolic acid is sufficient, provided equal parts of 
sputum and solution are mixed and the exposure continued for 24 hours. 
Ten per cent, lysol acts in 12 hours. Bichlorid of mercury is not ap- 
plicable for sputum disinfection, as it cannot penetrate the albuminous 
mass. Formalin, 10 per cent., may be used. 

Sunlight is one of the best germicides and often destroys tubercle 
bacilli quickly. In direct sunlight the bacilli die in a few hours, in 
diffuse sunlight in a few days, provided the sputum masses are not too 

Antiformin is a differential germicide, killing most non-spore-bear- 
ing bacteria, but acting more slowly upon the tubercle bacillus. Anti- 
formin is a strongly alkaline solution of sodium hypochlorite. (Page 


Preventive measures are based upon two important facts : that tu- 
berculosis is an infection mainly spread from man to man through 
direct association, and secondarily from cattle through infected milk. 
Preventive measures fall into two categories: (1) avoiding the infec- 
tion, and (2) increasing resistance through personal hygiene. Both 
are necessary. The infection may be avoided through segregation; the 
use of milk from tuberculin-tested cattle, else pasteurized; education; 

' The thermal death point of pathogenic microorganisms in milk. M. J. 
Rosenau, Hyg. Lab. Bull. U. S. Pub. Health and Mar. Hosp. Serv., No. 42. 


disinfection; proper disposal of tuberculous sputum; the avoidance of 
contact with open cases, especially with those who do not use proper 
precautions; early diagnosis, etc. Increased resistance may be gained 
through fresh air, good food, rest, and compliance with the dictates of 
personal hygiene. This part of the subject includes sociologic and 
economic reforms, without which the warfare against tuberculosis can- 
not succeed. Improvement in housing conditions, lowering of the cost 
of living, increase in the scale of wages, and all forms of uplift help 
secondarily to diminish the amoi;nt of the disease. Furthermore, it Avill 
be necessary to consider secondary agencies, as preventive clinics, indus- 
trial insurance, notification, open-air schools, day and night camps, etc. 

It is well to remember that tuberculosis has gradually declined in 
England and also in ]\Iassachusetts since about 1850 — before the tu- 
bercle bacillus was discovered. 

Segregation. — ^Tuberculosis is a "contagious" disease, and it is now 
perfectly plain that one of the most important single preventive meas- 
ures in this as in all other communicable diseases consists in isolation. 
A case isolated is a case neutralized, hence the great value to the com- 
munity of sanitarium treatment. Isolation in this case refers only to 
those individuals having tubercle bacilli in their sputum, and especially 
to the advanced and helpless cases. The isolation in tuberculosis need 
not go to the extreme practiced in the acute communicable fevers. In 
fact, we cannot for many 3-ears to come object to giving a case of open 
pulmonary tuberculosis his complete liberty, provided he is careful 
and cleanly and uses proper precautions in the disposal of his expectora- 
tion. When the disease becomes less prevalent more stringent and ar- 
bitrary measures may then be enforced. 

'•'Every case of tuberculosis isolated means an average of at least 
three less new infections." Sanatoria should, therefore, be attractive 
and as cheap as it is possible to run them. Free hospital care for 
the incurable cases is necessary, especially for the poor. Tuberculosis 
has diminished most in those countries where sanatoria are most in use. 

Personal Prophylaxis. — Personal prophylaxis consists in avoiding the 
infection and in obeying all the dictates of personal hj^giene — that is, 
living a clean, normal, and temperate life. 

Close association with persons known to have tubercle bacilli in 
their sputum is hazardous. This becomes especially dangerous when 
the contact is prolonged and intimate, such as working in the same 
room, especially if it is small and ill-ventilated, or sleeping in the 
same bed. The more intimate the association and the less care the tu- 
berculous individual takes with the expectoration, the greater is the 
danger. The infection may further be avoided by refusing to drink 
from common cups, by taking care in placing objects to the mouth that 
do not belong there, by avoiding dusty atmospheres, and refusing to 


drink milk that docs not come from tuberculin-tested cattle unless it is 

Meclianical obstructions to breathing should be corrected, by surgical 
methods if necessary. Functional lack of proportion in the chest and 
lungs of young people favor infection, and every effort should be made 
to help the child to outgrow them. Breathing exercises and outdoor 
play are especially useful. 

A generous diet is one of the best prophylactics against tuberculosis. 
A fat-rich food favors the development of a water-poor body, and it is 
known from experimental observation that animals with the largest pro- 
portion of water in their tissues yield to infection more readily than 

Resistance to the disease is increased by rest, fresh air, good food, 
sunshine, the avoidance of all depressing influences, such as worry, 
overwork, intemperance, and excesses of all kinds. Attention should 
be given to slight colds and other conditions known to be predisposing 
causes to the disease. 

Education. — The prevention of tuberculosis, like all other wide- 
spread infections, depends for its success upon the education of the 
people. We are now in possession of sufficient information of a pre- 
cise nature to place the facts in plain words before the pul)lic. This 
has been done in numerous excellent, pamphlets and popular articles in 
the daily press and magazines, through lectures, exhibits, and meet- 
ings, so that there is now a widespread and correct understanding of 
the proldem. The modern message in tuberculosis has been one of 
hope, in that the disease is curable; and one of fear, in that it is trans- 
missible. The former has been a great encouragement and has added 
strength to the movement; the latter is also helpful, although it has 
run to extremes in some quarters. An unwarranted fear of tubercu- 
losis (phthisiophobia) has subjected the tuberculous individual to se- 
vere hardships by branding him as a leper. Even cured cases of the 
disease now find difhcidty in obtaining work, A wholesome regard for 
the infection is useful and helpful in preventive medicine, but an hys- 
terical fear of tuberculosis is quite as unwarranted as a total disregard 
for the infection. 

Notification. — Tuberculosis should be included among the list of 
diseases requiring compulsory notification. ' Without this important fea- 
ture preventive measures are handicapped. The objection to compul- 
sory notification is based largely upon sympathy with the large num- 
ber of individuals affected and the sensitiveness of the afflicted. Com- 
pulsory notification may result in unnecessary harm, in that the knowl- 
edge of the fact may result in loss of occupation and an avoidance by 
his fellowmen on account of the fear people now have of associating 
with a tuberculous individual. These effects may, for the present, be 


neutralized by considering the records as confidential communications 
between physician and health officer. 

Tuberculosis is required to be reported in Maine, Michigan, Massa- 
chusetts (since 1907) ; many cities: Alameda, California; Asbury Park, 
N. J. ; Boston, Buffalo, Cincinnati, New York, Salt Lake City, Trenton, 
Yonkers — also in Washington, D. C, Minneapolis, San Francisco, and 
Syracuse. The list is growing and the returns are gradually improving. 

Disposal of the Sputum. — As the tuberculous sputum is the principal 
source of the infection, it should be disinfected or disposed of so that 
it will be harmless to others. Perhaps the best way is to receive the 
expectorated matter into cloths,* which may be burned, or the material 
may be received into one of the various forms of sputum cups and 
finally burned or disinfected. Persons with pulmonary tuberculosis 
must be warned against the possible danger to others of coughing with- 
out holding the handkerchief before the mouth and nose; under no cir- 
cumstances should they spit upon the floor. Penalty for spitting upon 
the sidewalk, upon the floor of public buildings, and in street cars serves 
a useful purpose in diminishing the spread of tuberculosis as well as 
other diseases. 

In sanatoria and hospitals the infected material may be burned or 
disinfected with steam under pressure in a special autoclave, or disin- 
fected with phenol (5 per cent.), lysol (2 per cent.), tricresol (2 per 
cent.), or formalin (10 per cent.). 

Disinfection. — Eooms occupied by tuberculous individuals should be 
kept clean and disinfected from time to time. A thorough disinfec- 
tion and cleansing should also be practiced before such rooms are oc- 
cupied by other persons. This may be accomplished by mopping sur- 
faces with the usual solutions of bichlorid of mercury or one of the 
coal-tar preparations, followed by formaldehyde fumigation and a me- 
chanical cleansing, and then a thorough airing and sunning. 

Early Diagnosis.— Early diagnosis plays an important role in suc- 
cessful prevention; not only does it give the individual the best chances 
of cure, but at the same time it assures the possibility of maximum 
protection to others. Through the use of tuberculin and through re- 
finements of clinical methods it is now possible to diagnose tubercu- 
losis at a stage when it was formerly not suspected. It is a great mis- 
take, from the standpoint of prevention, to wait until tubercle bacilli 
appear in the sputum before making a diagnosis of tuberculosis. Prob- 
ably many cases of "a slight run-down condition," of transient and 
irregular febrile attacks, are due to a small focus of tuberculosis hid- 
den from the ken of the clinician. In such cases a course of rest, 
fresh air, and better food, with a change of scene, may often prevent 
irreparable damage. The establishment of preventive clinics to look 
after such cases and the maintenance of medical clinics to diagnose and 


care for the early cases are important adjuncts to preventive measures. 
Housing Conditions. — It has long been realized, even before the rea- 
sons were understood, that improvement in housing conditions dim- 
inishes the incidence to tuberculosis. This is a common observation 
in the stabling of cattle as Avell as the domicile of man. The reasons 
why improving the housing conditions diminishes the spread of tuber- 
culosis are complex. In addition to raising the standard of living, 
better houses diminish the chances of contact infection, afford better 
air and more sunshine, and tend generally to the well-l)cing and up- 
lift of mankind. ]\Iunieipalities do well to enact and enforce stringent 
laws regulating the construction of houses, offices, stores, and work- 
shops. The congested and squalid slums are both a disgrace and a 
menace. Germs are social climbers, and many a palace is invaded with 
an infection from a nearby neglected alley. Philanthropists cannot do 
better than assist in improving the housing conditions of the poor. 

Bovine Tuberculosis. — The prevention of bovine tuberculosis con- 
sists simply in using milk, cream, and fresh milk products from tu- 
berculin-tested cattle. The cattle should be tested frequently; at least 
twice a year, for the disease may develop in the cow in a few months. 
WTien milk is used from non-tested cattle, it should be pasteurized, and 
the same precaution applies to the milk used for making cream, but- 
ter, ice-cream, and other fresh milk products. 

Industrial Insurance.- — ^Industrial insurance patterned after the plan 
used in Germany is a useful adjunct in the tight against tuberculosis. 
The German industrial associations under government supervision do 
more than care for the tuberculous workman. The heavy drains upon 
the funds of the industrial associations have been checked by the estab- 
lishment of "preventoria." These are attractive country places where 
the working man can go when he is "run down." This simple meas- 
ure is a great boon, and prevents the development of many a case of 
tuberculosis as well as other diseases. 

Day camps, night camps, visiting nurses, and similar agencies are 
all helpful. In addition to the direct benefits, they teach the patient 
how to prevent the spread of the infection, how to sleep out of doors 
and its benefits. 

The prevention of tuberculosis is no longer a medical problem — 
rather a sociological problem. The battle against tuberculosis has been 
waged with enthusiasm and the results arc encouraging. Its eradica- 
tion will, however, take a long time on account of the chronic nature of 
the disease and its widespread prevalence. We should be satisfied if we 
diminish the amount of tuberculosis appreciably in a generation. The 
momentum thus gained will increase rapidly. The time will then come 
when the comparatively few cases left may be treated by compulsory 
isolation or other aggressive measures. Persistence along the lines now 


understood will in time control the disease, which will be the crowning 
achievement in preventive medicine. 


Our knowledge of diphtheria is most satisfactory in that we know 
the cause of the disease and its modes of transmission ; we are able to 
check its spread, and possess a specific preventive and curative agent of 
great potency. 

Diphtheria spreads slowly from person to person and from com- 
munity to community. It is not necessary to consider it endemic in 
special indigenous foci, because it is seldom completely absent in any 
large community. ISTewsholme points out that diphtheria epidemics 
and pandemics occur cyclically. The intervals between the years of epi- 
demic prevalence vary greatly. In Boston diphtheria was epidemic in 
1863-64, 1875-76, 1880-81, 1889-90, and 1894; in New York in 1876- 
78, 1880-82, 1886-88, and 1893-94; in Chicago in 1860-65, 1869-70, 
1876-79-81, 1886-87, and 1890. The causes of these epidemic out- 
bursts are not clear. They may be due to a fortuitous combination 
of such circumstances as a new crop of susceptible children, a particu- 
larly virulent strain of the bacillus, the opening of the' schools, and 
similar factors favoring the spread of the infection. On the other 
hand, external conditions, such as dryness, may be important, for "diph- 
theria only becomes epidemic in years in which the rainfall is deficient. 
There is no instance of a succession of wet years in which diphtheria 
was epidemic." It is more than likely that the great outbreaks are due 
to a combination of the three factors — man, the bacillus, and the en- 
vironment. Just as a spark in a forest may cause a brush fire or a con- 
flagration, depending upon the amount of vegetable growth, its distribu- 
tion, its condition as to dryness, the direction and force of the wind, the 
topography and nature of the soil, and a thousand and one other con- 
ditions, so diphtheria and other infections will smolder or burst into 
flame, ' depending upon many factors. 

Diphtheria is said to prevail more in rural than in urban dis- 
tricts. Sir George Buchanan first pointed out that it has always dis- 
played a more marked tendency to prevail in sparsely settled districts 
than in centers of population, although outbreaks in congested centers, 
schools, camps, on board ships, and in other crowded places, are common. 
In the tropics diphtheria is practically absent. ISTewsholme pointed out 
that it is more of a continental than an insular disease. 

The fatality from diphtheria has been greatly lowered since 1904, 
owing to the use of antitoxin and owing also to refinements of diagnosis, 
as a result of which many mild cases are now included that were formerly 
omitted from the statistical records. Whether or not there has been a 



natural tendency for the disease to become milder in recent years can- 
not be stated. 

Diphtlieria reaches its maximum prevalence in the autumn of each 
year,, which corresponds to the seasonal prevalence of scarlet fever. 

In 1878 Dr. Thrushfield 
published papers illustrating 
the way in .which diplitlieria 
hung about damp houses. A 
damp dwelling favors sore 
throats and colds, and may 
thus open a way for invasion 
of the bacilli, just as any de- 
pressing influence may pre- 
dispose to the infection. Chil- 
dren with scarlet fever or 
measles are especially prone 
to take diphtheria if the in- 
fection is around. Formerly 
imperfect drains and sewer 
gas were given as the causes 
of diphtheria ; this is a fetish 
which dies hard. 

Modes of Transmission. 
— The diphtheria bacillus 
almost always enters by the 
mouth or nose, and the 
lesions are usually localized 
in the mucous membranes of 
the throat, nose, larynx, or 
upper respiratory tract. The 
bacillus leaves the body in the 
discharges from the mouth 
and nose. Diphtheria occa- 
sionally affects other mucous 
membranes or abraded sur- 
faces, such as the conjunctiva 
or vaginal mucous membrane, 
or open wounds, in which case the discharges from these lesions contain 
the infection. 

The bacillus may be transmitted directly from one person to an- 
other, as by kissing, or exposure to droplet infection in coughing, speak- 
ing, and sneezing; or the infection may be conveyed indirectly from 
one person to another in a great variety of ways; most common among 
children, perhaps, are toys, slate pencils, food, fingers, handkerchiefs, 






















































Fig. 16. — Ch.\rt Computed from the Un'ited 
States Census Report to Show how the 
Opening of the Schools in Autumn In- 
creases Diphtheria. 

The broken line shows the number of cases among 
school children five to fourteen years old 
during 1900-04 in the registration area of the 
United States. The unbroken line shows the 
number of cases among children, from birth 
to five years of age, for same period and area. 

On this chart the augmented increase in diphtheria 
among school children from five to fourteen 
years of age, as compared with children 
under five years, is strikingly shown. 

(Mass. State Board of Health, Monthly Bull, Sept., 


or other objects that have been mouthed first by the infected child and 
then by the susceptible child. Experience points clearly to the conclu- 
sion that diphtheria infection is transmitted usually l^y direct exchange 
of the flora of the nose and throat, rather than through inanimate 

Bacillus carriers play a large role in spreading the infection. Milk 
and other foods may become infected and transmit the disease. 

The diphtheria bacillus is frail and soon dies when dried or ex- 
posed to sunlight, therefore air-borne infection is probable only in the 
case of close association, that is, within a few feet of the infected per- 
son and within the radius of the possibility of droplet infection. 

The following description by Chapin illustrates how diphtheria 
and all other infections contained in the secretions from the mouth 
and nose may be transmitted ; it also emphasizes the importance of edu- 
cation in personal hygiene based upon habits of biological cleanliness: 

"Not only is the saliva made use of for a great variety of purposes, 
and numberless articles are for one reason or another placed in the 
mouth, but, for no reason whatever, and all unconsciously, the fingers 
are with great frequency raised to the lips or the nose. Wlio can doubt 
that if the salivary glands secreted indigo the fingers would not con- 
tinually be stained a deep blue, and who can doubt that if the nasal 
and oral secretions contain the germs of disease these germs will not 
be almost as constantly found upon the fingers? All successful com- 
merce is reciprocal, and in this universal trade in human saliva the 
fingers not only bring foreign secretions to the mouth of their owner, 
but there, exchanging it for his own, distribute the latter to everything 
that the hand touches. This happens not once, but scores and hun- 
dreds of times, during the day's round of the individual. The cook 
spreads his saliva on the muffins and rolls, the waitress infects the 
glasses and spoons, the moistened fingers of the peddler arrange his 
fruit, the thumb of the milkman is in his measure, the reader moistens 
the pages of his book, the conductor his transfer tickets, the 'lady' 
the fingers of her glove. Everyone is busily engaged in this distribu- 
tion of saliva, so that the end of each day finds this secretion freely 
distributed on the doors, window sills, furniture, and playthings in the 
home, the straps of trolley cars, the rails and counters and desks of 
shops and public buildings, and, indeed, upon everything that the hands 
of man touch. What avails it if the pathogens do die quickly? A 
fresh supply is furnished each day. Besides the moistening of the 
fingers with saliva and the use of the common drinking cup, the mouth 
is put to numberless improper uses which may result in the spread of 
infection. It is used to hold pins, string, pencils, paper, and money. 
The lips are used to moisten the pencil, to point the thread for the 
needle, to wet postage stamps and envelopes. Children Wap' apples;, 


cake, and lollipops, while men exchange their pipes and women their 
hat pins. Sometimes the mother is seen 'cleansing' the face of her 
child with her saliva-moistened handkerchief, and jierhaps the visitor 
is shortly after invited to kiss the little one. 

"Children have no instinct of cleanliness, and tlieir faces, hands, 
toys, clotliing, and everything that they touch must of necessity he 
continually dauhed with the secretions of the nose and mouth. It is 
well known that children between the ages of two and eight years are 
more susceptible to scarlet fever, diphtheria, measles, and whooping- 
cough than at other ages, and it may be that one reason for this is the 
great opportunity that is afforded by their habits at these ages for the 
transfer of the secretions. Infants do not, of course, mingle freely 
with one another, and older children do not come in close contact in 
their play, and they also begin to have a little idea of cleanliness." 

Milk-borne Diphtheria. — The diphtheria bacillus grows well in 
milk without appreciably changing its flavor or appearance. Trask col- 
lected 23 diphtheria epidemics from the literature between 1895 and 
1907. Fifteen of these occurred in tlie United States and 8 in Great 
Britain. The milk is usually contaminated by cases of the disease occur- 
ring on the farm or at the dairy or milk shop. In some cases the diseased 
person milks the cows or the same person nurses the sick and handles 
the milk. In two instances the outbreak was supposed to be due to 
disease of the cow. One of these instances studied by Dean and Todd 
is instructive. In certain families supplied with milk from two cows 
there occurred two cases of clinically typical diphtheria and three of 
sore throat, whereas in another family using the milk, only after sterili- 
zation, no case occurred. One of the cows had mammitis and furnished 
a scanty, ropy, semi-purulent, and slightly blood-tinged milk. The 
Klebs-Loffler bacilli were isolated in all cases and also from the milk 
of the cow with mammitis. Experiments justified the conclusion that 
the ulcers upon the udder of the cow with mammitis had become secon- 
darily infected with B. diplitJierice, probably accidentally from some ap- 
parently healthy person. 

As a rule diphtheria epidemics caused by infected milk are more 
limited both as to numbers and area than milk-borne outbreaks of ty- 
phoid or scarlet fever. 

Bacillus Carriers. — It was in the case of diphtlicria that tlie dan- 
ger of bacillus carriers was first realized. It is now known that per- 
sons who come in contact with diphtheria patients are very apt to 
harbor diphtheria bacilli, though they may remain in good health. It 
is also now well known that a certain percentage of the population 
at large harbor the diphtheria bacilli in their nose or throat, even 
though they have had no known association with the disease. Graham- 
Smith found that 66 per cent, of the members of the family to which 


the diseased jDerson belonged were infected ; the proportion being higher 
(100 to 50 per cent.) in families in which no precautions were taken 
to isolate the sick, and much lower (10 per cent.) when such precau- 
tions were taken. Of the more distant relatives examined, 29 per cent, 
were found to be infected. Bacilli were found in 37 per cent, of per- 
sons in attendance on the sick. Observations of the inmates of hos- 
pital wards and institutions showed that 14 per cent, are likely to 
give positive cultures when diphtheria occurs among them. In in- 
fected schools 8.7 per cent, of the scholars were found to be bacillus 
carriers. In New York, Scholley examined 1,000 children from the 
tenement districts, and found 18 with virulent and 38 with non-viru- 
lent bacilli. Slack, Arms, Wade, and Blanchard took cultures at the 
beginning of the school year from about 4,500 pupils in the Brighton 
district, Boston. Diphtheria was not prevailing at the time. ISTever- 
theless, at least 1 per cent, of all these healthy school children were 
found to carry morphological typical diphtheria bacilli. It is estimated 
that this is the average ratio in the population at large. 

Ordinarily the bacilli found in diphtheria carriers under such cir- 
cumstances have little or no virulence. It is possible, but not very 
likely, that the virulence of such strains may be raised by passing 
through a susceptible individual. It is probable, however, that diph- 
theria is kept alive in a community rather by the virulent organisms 
in immune persons than by these non-virulent strains. None of the 
children in the Brighton district above mentioned had any known 
association with the disease, nor did they afterward develop diphtheria. 
The danger of such carriers is, therefore, problematic, and, on account 
of their large number, it is a question whether they should be isolated. 
The dangerous carrier is he who harbors the virulent strain, and this is 
usually obtained from the patient, convalescent, or from a third person 
who has come in contact with the patient. From our present standpoint 
it seems impractical to stamp out diphtheria from a large city by cul- 
tural tests of all its inhabitants and isolation of all carriers, especially 
where dependence is placed upon morphological diagnosis. Some harm- 
less bacteria have the morphological appearance of the diphtheria bacil- 
lus. On the other hand, the control of diphtheria outbreaks in institu- 
tions, camps, on shipboard, schools, and in similar places, where a num- 
ber of people are crowded together, as well as the control of epidemic 
outbreaks in cities and towns, depends eventually upon the recognition 
of carriers and their isolation. 

Park points out that diphtheria bacilli of like toxic power may 
differ in their liability to infect the mucous membrane. Virulence, 
therefore, has two distinct meanings when used in connection with 
the diphtheria bacillus. The virulence of the bacilli cannot be accu- 
rately determined from the severity of an isolated case. The most 


virulent bacillus found by Park was obtained from a mild case simu- 
lating tonsillitis. In localized epidemics tbe average severity of tbe 
cases probably indicates roughly tbe virulence of tlio l)acillus causing 
the infection. However, individual susceptibility and the character of 
the associated bacteria are important factors in determining the se- 
verity of the disease. 

The length of time it requires for diphtheria bacilli to disappear 
from the throat and nose varies greatly. Beebe and Park found that 
in 304 of 605 consecutive cases the bacilli disappeared within 3 days 
after the disappearance of the false membrane. In 176 cases they per- 
sisted for 7 days, in 64 cases for 12 days, in 36 for 15 days, in 12 
cases for 3 weeks, in 4 cases for 4 weeks, and in 2 cases for 9 weeks. 
In some instances the virulent organisms may remain for months. 
The disappearance of the bacilli from the throat and nose cannot be 
hastened by the usual injections of antitoxin, although Price states 
that diphtheria antitoxin applied locally hastens the disappearance of 
the bacilli. Diphtheria antitoxin, when injected subcutaneously, pro- 
tects the individual but does not harm the bacilli. Careful attention 
to the hygiene and cleanliness of the mucous membranes may hasten 
their disappearance, and this is favored by copious washing of the 
throat and nose with large volumes of physiological salt solution. Anti- 
septics, such as silver nitrate, applied locally seem to be of little service. 

In recent years other measures have been proposed to rid the mu- 
cous membranes of diphtheria bacilli. A serum containing agglutinins 
has been used with some success. This serum in powdered form is 
blown into the throat. The diphtheria bacilli are thereby agglutinated 
and may then be more readily washed away by gargling and douching. 
In case these procedures fail, a substance proposed by Emmerich known 
as "pyocyanase" may be used. This contains a ferment from bouillon 
cultures of the Bacillus pyocyaneiis. It is ai)plied locally and acts by 
its power of bacteriolysis. 

Encouraging results have recently been reported by "over-riding" 
the throats of diphtheria carriers with suspensions of Staphylococcus 
pyogenes aureus, which are sprayed into the throat and nose. The 
method was introduced by Schiotz in 1909. who reported the ])rompt 
disappearance of diphtheria bacilli in six carriers. Page, also Catlin, 
Scott and Day, Lorenz and Pavenel, and others, have reported success- 
ful results. 

Hewlett and Nankivell, and also Petruschky, report encouraging re- 
sults in clearing up diphtheria carriers by the subcutaneous injection of 
a diphtheria vaccine. 

We must acknowledge that all these measures often fail. The re- 
lief of bacillus carriers is one of the rewardful problems in preventive 


Resistance. — The diphtheria bacillus has less resistance to adverse 
conditions than the majority of the spore-free bacteria. It is more read- 
ily destroyed by light, heat, and disinfecting substances than the typhoid 
bacillus. In this regard it corresponds more to the frailer streptococci. 
Under certain circumstances the diphtheria bacillus resists drying for a 
long time. When buried in the false membrane or other albuminous 
substances, they may remain virulent for some months. 

Immunity. — Immunity to diphtheria is very largely an antitoxic im- 
munity and persists for some months or years following a natural attack 
of the disease. Frequently immunity is of short duration, and second 
and third attacks are not uncommon. The fact that healthy persons 
may harbor virulent bacilli upon their mucous membrane for a long 
time without contracting the disease shows that other factors are in- 
volved. These predisposing causes are inflammations or lesions of any 
kind of- the mucous membrane, depressed vitality due to bad air, over- 
crowding, poor food, etc. Persons vary markedly in susceptibility. 
During the first 6 months of life there is but little susceptibility. 
Children between the ages of 3 and 10 are most susceptible ; after that 
age the susceptibility again decreases. It is known that guinea-pigs 
born of immunized mothers inherit a certain degree of resistance, which 
may explain the relative insusceptibility of children under 6 months. 
This may also be accounted for by the diminished danger of exposure 
of babies during this age, especially in those that are breast-fed. Moth- 
er's milk, even colostrum, contains protective antibodies, which are ab- 
sorbed by the infant, and thus may protect it. 

Prevention. — Control of Outbreaks in Institutions. — Diphtheria 
frequently appears in asylums, hospitals, jails, on shipboard, and similar 
places. Under these conditions of crowding the disease has a highly 
contagious tendency. It may, however, be controlled with every as- 
surance of success by the application of well-tried measures. It is cus- 
tomary first of all to give a prophylactic dose of antitoxin to all the 
persons within the institution, including both inmates and adminis- 
trative force. This, however, must be regarded more as a measure of 
temporary personal protection than as a radical means of stamping out 
the infection. It is not possible by the use of diphtheria antitoxin 
alone to wipe out diphtheria. The bacilli remain in the throats of the 
immunized and the disease continues to crop out after the antitoxic 
immunity has passed away, which may be a matter of only a few 
weeks. When diphtheria, antitoxin is used as a prophylactic, the dose 
is 1,000 units, which should be repeated every ten days or two weeks — 
as long as the danger persists. 

The most important measure to suppress diphtheria in an institu- 
tion is to isolate all cases and all carriers. This is possible in an in- 
stitution, although not very practical among the population at large. 


The isolation of both cases and carriers is the most important and radical 
of our preventive measures. In the case of institutions, jails, ships, 
and similar places all those who show cultures containing organisms 
which morphologically resemble tlie diphtheria bacillus should be iso- 
lated, w'hether the strains are virulent or not. 

The bacilli frequently grow in the mucous membrane of the nose 
and nasal pharynx without symptoms indicating their localization. Un- 
less cultures are taken from the nose, many carriers will be overlooked, 
leaving a large loophole in our preventive measures. Ward and Hen- 
derson in a public school epidemic in Berkeley in 1907 found that all 
attempts to isolate infected children had no effect on the epidemic so 
long as they made throat cultures alone. When they took bolli nose 
and throat cultures and quarantined all the children showing positive 
cultures, the epidemic stopped. 

Convalescents should not be released from quarantine until at least 
two cultures taken from both the nose and throat are negative. 

In addition to the above-mentioned measures, care must be taken 
that the infection is not spread by the use of cups, spoons, dishes, 
towels, handkerchiefs, and other articles used in common. The in- 
fected discharges should be rendered harmless at the bedside, and all 
objects that come in contact with patients or carriers should be disin- 
fected. A general disinfection with formaldehyde may be practiced, 
but in a well-ordered institution the usual cleanliness of floors, walls, 
and other surfaces will suffice. 

Control of Epidemics. — The principles which guide us for the con- 
trol of outbreaks among the population at large are precisely the same 
as those described for the control of epidemics in institutions. The 
only difference is that in the population at large it is more difficult, 
if not impossible, to apply the one real important measure, namely, 
that of isolating the carriers. What is needed is a convenient and re- 
liable method of distinguishing the virulent and dangerous bacilli from 
those that look like diphtheria bacilli but lack pathogenic power and 
danger to man. 

In almost all communities diphtheria is now one of the diseases 
which must be reported to the health authorities. The houses are 
placarded and the cases isolated. There is no great objection to treat- 
ing a case of diphtheria in the household provided the patient and the 
nurse may also be quarantined from the rest of the household. Under 
these circumstances and with intelligent care and disinfection at the 
bedside there is little danger to the rest of the family; but the great 
menace that some of the members of the family will harbor bacilli of 
a dangerous type and transmit them to others makes it advisable to 
treat all cases of diphtheria in a special hospital. 

The prompt and early diagnosis of diphtheria has now become one 


of the routine measures of board of health laboratories. This example 
in the case of diphtheria could be extended with advantage to the other 
communicable diseases for which we have satisfactory laboratory aids. 
Especially commendable is the general practice of refusing to lift the 
quarantine until two successive cultures prove negative. 

Disinfection in diphtheria should be applied especially to the se- 
cretions from the mouth and nose. These may be received upon a piece 
of gauze and burned. For the hands and other objects bichlorid of 
mercury (1-1,000), carbolic (2^/2 per cent.), formalin (10 per cent.), 
tricresol (1 per cent.), are efficient. As a terminal disinfectant for- 
maldehyde gas may be used, but the ordinary fumigation, as practiced 
by Boards of Health, seems to have little influence in checking the 
spread of the disease. Evidence is accumulating that the infection 
usually comes from persons rather than from things. Bed linen, towels, 
and other fabrics should be boiled or steamed. 

Personal Prophylaxis. — In individual cases diphtheria may be 
avoided by the use of diphtheria antitoxin. The antitoxic immunity, 
however, depends upon the free circulation of the antibodies in the 
blood, and as the antitoxin is gradually eliminated it cannot be de- 
pended upon to protect more than 2 or 3 weeks. 

Diphtheria antitoxin is a specific and sovereign remedy. When given 
in sufficient amounts during the first 24 hours of the disease it reduces 
the mortality to practically nil. Ordinarily 500 units . are sufficient 
for prophylactic purposes, but 1,000 units are preferable, as this amount 
produces an immunity of higher degree and longer duration. When 
the exposure to the infection continues the antitoxin may be adminis- 
tered at successive intervals of about 2 or 3 weeks. Upon the first ap- 
pearance of sore throat, fever, or other suggestive symptoms in persons 
who are exposed to diphtheria a full dose of 3,000 to 10,000 units should 
be administered without delay. In order to obtain the full life-saving 
benefits of diphtheria antitoxin, it should be given early in the disease. 
Time is the most important factor. When the damage to the cells 
has been done, it may be too late. It is not always advisable to 
wait for bacterial confirmation. Personal prophylaxis is further fa- 
vored by the individual having his own glass, cups, spoons, towels, etc., 
and exercising personal cleanliness, especially concerning the hands 
and all objects placed in the mouth. Physicians, nurses, and others 
who come in close contact with the patient should guard against drop- 
let infection. 


It has been observed that post-diphtheritic paralysis is more fre- 
quent since the use of antitoxin than before the days of serum therapy. 


This is due to the fact that many cases now recover that would for- 
merly have died. It is also due to the fact that diphtheria antitoxin 
is sometimes used too late, thus neutralizing only the acute effects of 
the toxin, but not neutralizing the after-effects of the toxon, which 
acts specifically upon the nerves. The prevention of post-diphtheritic 
paralysis, therefore, consists in giving sufficient amounts of antitoxin 
early in the disease. The antitoxin does not influence the paralysis 
after it has once appeared. 


This subject may appropriately be considered here, although it is 
a condition that may follow the injection of any alien serum into 
the system. Serum sickness is a syndrome which frequently follows 
the injection of horse serum into man. The symptoms come on after 
about 8 or 10 days following the injection. They consist of various 
skin eruptions, usually urticarial or erythematous in character; also 
fever, edema, glandular enlargements, rheumatic-like pains in the joints, 
and albuminuria. The eruptions may be either local or general, and 
sometimes resemble that of scarlet fever or measles. Serum sickness 
has nothing to do with the antitoxin, but is caused entirely by the 
foreign proteins contained in the horse serum. It may be produced 
with normal horse serum as well as with antitoxic horse serum. The 
studies upon anaphylaxis have thrown much light upon the nature of 
this complication. The serum of some horses is much more apt to 
produce the syndrome than that of other horses. A serum that is sev- 
eral years old is perhaps less apt to produce these reactions than a 
fresh serum. Manufacturers of antitoxin, therefore, prefer to keep 
their serum in the ice chest some time before they place it upon the 
market, although this a doubtful expedient. The occurrence and severity 
of the symptoms are in direct proportion to the amount of foreign pro- 
tein injected. Fortunately, this form of anaphylactic reaction soon 
passes away and is never serious. Under certain circumstances, however, 
there may be an accelerated or immediate reaction threatening in its 
consequence or even leading to death. Rosenau and Anderson have col- 
lected some 19 cases of sudden death following the injection of horse 
serum, and they know of more instances which have not appeared in the 
literature. This unusual and serious complication comes on within 5 
or 10 minutes of the injection, and is characterized by collapse, uncon- 
sciousness, cyanosis, labored respiration, and edema. The heart continues 
to beat after respiration has ceased. The entire picture is an exact 
counterpart of the anaphylactic shock so readily reproduced by second 
injection of horse serum or other foreign protein in the guinea-pig. Con- 
trary to the experimental work on the lower animals, most of the cases of 


sudden death in man follow the first injection of horse serum. The seri- 
ous symptoms and death in these cases are not due to any inherent poison- 
ous property in the antitoxic serum, but result entirely from a hyper- 
susceptibility of the individual. Just how man becomes sensitized 
in these cases is not known. Most of the cases, however, occur in 
asthmatics or in persons who gave a history of asthma or discomfort 
when about horses. This is a practical and important point, and should 
be inquired into before horse serum of any kind is injected. Horse 
serum should not be injected into such individuals unless the indica- 
tions are clear, and then only with a statement as to the possible out- 

In order to prevent this serious complication a small quantity 
may first be injected, 1 or 2 drops, and after waiting an hour the re- 
mainder may be given. Vaughan proposed 0.5 c. c. as the trial dose, 
but this is excessive, as some of the fatal cases have followed the in- 
jection of about 1 c. c. It is known that in man, as in the experi- 
mental cases in the guinea-pig, the severity of the symptoms bears a 
definite ratio to the amount of serum and the mode of injection. Thus, 
second injections in the guinea-pig are much more fatal when given 
directly into the circulation than into the subcutaneous tissue. It is 
sometimes advisable to give antitoxic sera directly into the circula- 
tion, but in the susceptible persons under discussion this would be 

Friedberger and Mita ^ found it possible to avoid all symptoms of 
anaphylaxis in experimental work with guinea-pigs by injecting the 
serum extremely slowly. When thus introduced animals are able to 
tolerate an amount far beyond the ordinary lethal dose. 

Historical Note. — A complete summary and bibliography of diph- 
theria up to 1908 will be found in the system edited by Nuttall and 
Graham-Smith entitled "The Bacteriology of Diphtheria," containing 
articles by Loffler, ISTewsholme, Mallory, Graham- Smith, Dean, Park, 
and Bolduan; Cambridge University Press, 1908. 

The original clinical description of the disease is, by common as- 
sent, attributed to Bretonneau in 1826 : Traite de la diphtherite. Des- 
inflammations speciales du tissu muqueux et en particulier de la diph- 
therite ou inflammation pelliculaire, connue sous le nom de croup, d'an- 
gine maligne, d'angine gangreneuse, etc., Paris. 

The bacillus of diphtheria was first cultivated and adequately de- 
scribed by Loffler, 1884 : Untersuchungen iiber die Bedeutung der 
Mikroorganismen fiir die Entstehung der Diphtheric beim Menschen 

' Friedberger, E., and Mita, S. : "To Prevent Anaphylaxis in Serotherapy ' ' 
("Methode, grossere Mengen artfremden Serums bel iiberempfindlictien Indi- 
viduen zu injizieren"), Deutsche med. Wochenschr., Berlin, Feb. 1, XXXVIII, 
No. 5, pp. 201-248. 


bei der Taube und beim Kalbe. Mitth. a. d. K. Gesundheitsamte, ii, 

The classical article in which Behring and Kitasato announced 
their discovery of diphtheria antitoxin in 1890 will be found in Deutsche 
nied. Wochenschr.. xvi, 1113. Ueber das Ziistandekommen der Diph- 
therieimraunitat und die Tetanusimmunitat bei Tieren. 

Ehrlich's important work, in which he laid the foundations of his 
side-chain theory and established the present satisfactory method of 
standardizing diphtheria antitoxin, will be found in the following: 
Die Werthbemessung des Diphtherieheilserums und deren theoretische 
Grundlagen. Klin. Jahrb., Jena, v, 6 (2), 1897, pp. 299-326. Ueber 
die Constitution des Diphtheriegiftes. Deut. nied. Woch., Leipzig, v, 
24 (38), 1898, pp. 597-600. Croonian lecture. On Immunity with 
Special Reference to Cell Life. Proc. Roy. Soc, London, v, 66, pp. 
424-448, pis. 6-7. 

The official method for standardizing diphtheria antitoxin in this 
country and the principle upon which it is based are described by 
Rosenau (1905), The Immunity Unit for Standardizing Diphtheria 
Antitoxin (based on Ehrlich's normal serum). Hygienic Laboratory 
Bull. No. 21, P. H. and M. H. S., Washington, Govt. Print. Office, 92 pp. 


Measles is usually taken as the type of a contagious disease because 
it is one of the most readily communicable of all diseases, in this re- 
gard ranking with smallpox. As a cause of death it ranks high among 
the acute fevers of children. Measles is an infection peculiar to man, 
although experimental measles has recently been produced in monkeys. 
The virus is contained in the blood, as has been shown by Hektoen, 
who thus transmitted the disease from man to man. More important 
from the standpoint of prevention, the virus has been demonstrated in 
the secretions from the nose and mouth by Anderson and Goldberger. 
The period of incubation is quite constant (from 9 to 11 days), and 
the rash appears quite uniformly on the 13th or 14th day after the 
infection. In Hektoen's two experimental cases the eruption appeared 
on the 14th day. The cause of measles is not known. 

Measles is more or less constantly present in all large cities in 
the temperate zone ; it is less common in the tropics. Measles fre- 
quently becomes epidemic, usually in the cooler months, in this respect 
resembling smallpox. The epidemics recur cyclically, at irregular in- 
tervals. Levy and Foster noticed that in Richmond, Va., epidemic 
outbreaks recurred at intervals of about 3 years. They were able to 
predict and warn against an epidemic prevalence of the disease in the 


winter of 1910. During 1909, iO cases of measles occurred in Eich- 
mond, but during this year the disease showed no special tendency to 
spread. In the middle of February, 1910, 8 cases occurred among the 
pupils of one school and the infection showed a high degree of com- 
municability. According to the history of the disease, an epidemic year 
was due and an epidemic was predicted. Over 2,000 cases occurred 
with 26 deaths. 

Measles is highly contagious during the preeruptive stage, when 
the nature of the disease is not recognized and when most of the dam- 
age is done; it remains contagious for a variable time during conva- 
lescence. Eecent experimental evidence and clinical experience plainly 
indicate that the infection of measles soon dies out, and that there is 
little danger of transmitting the infection after the temperature re- 
turns to normal. An isolation of two weeks from the onset of the dis- 
ease is sufficient in public health work; health officers, however, adopt 
arbitrary times. Thus, in Detroit cases of measles are isolated one 
week; in Buffalo, Concord, Xew York, Providence, and Yonkers, two 
weeks ; in Brookline and Fall Eiver, two weeks after the eruption fades ; 
in Boston, two weeks after recovery; and three weeks in Montclair, 
X. J., Xew Bedford, Mass., Ottumwa, Iowa. 

Immunity. — One attack of measles usually confers a rather definite 
protection against subsequent attacks; second attacks, however, are 
more common than in the other eruptive fevers. Some persons have 
the disease three or four times. As with smallpox, there appears to be 
no natural immunity to measles — man is excjuisitely susceptil^le to these 
two infections. There appears to be a relative immunity sometimes of 
a high grade during the first few months of life, although measles oc- 
casionally occurs in infants of a month or six weeks. 

Adults are susceptible to measles, provided they have not had a 
previous attack. Susceptibility to the infection does not diminish with 
increasing age; the disease is apparently one of childhood only on ac- 
count of the chances of exjDOsure in early life. Before the days of vac- 
cination smallpox was also a disease mainly of childhood. 

The following instances demonstrate the suscei^tibility of adults to 
measles and also the serious nature of the disease : Measles was intro- 
duced into the Faroe Islands in 1816 from Copenhagen, and over 6,000 
of the 7,782 inhabitants were stricken. In 1775 it was introduced into 
the Sandwich Islands, and in 4 months 40,000 of the population of 
150,000 died. 

Measles is common in army camps, especially among troops enlisted 
from country districts, who are thus exposed to the infection for the 
first time. 

Measles is often fatal both in adults and children on account of 
pneumonic complications. It also seems to lower the resistance to tu- 


berculosis; for it is a common history to find tuberculosis develop in 
children following an attack of measles. 

Resistance of the Virus. — In general the virus of measles is known 
to be much less resistant than that of scarlet fever and many other in- 
fections. The virus does not live long upon fomites. There is prac- 
tically no danger of children contracting the infection from the room 
in which the patient was treated, even though no disinfection was 
practiced, provided two weeks have elapsed. 

Goldberger and Anderson ^ found, as the result of experiments upon 
monkeys, that the virus in measles' blood is filterable; that is, may pass 
through a Berkefeld filter. It resists desiccation for 251/^ hours, loses 
its infectivity after 15 minutes at 55° C, resists freezing for 25 hours, 
and possibly retains some infectivity after 24 hours at 15° C. 

From the standpoint of our present knowledge it is evident that 
any of the ordinary germicidal agents sufficient to kill spore-free bac- 
teria will serve as effective disinfectants for measles. Aside from the 
few scientific observations upon the viability of the virus of measles, 
epidemiological observations have long pointed out the fact that the 
virus of measles is frail and soon dies in the convalescent as well as in 
the environment. 

Modes of Transmission. — The virus of measles is contained in the 
nasal and buccal secretions. \Miile it is possible that the virus may 
leave the body in other secretions, it is highly probable that the dis- 
charges from the nose and mouth are the means of transmitting the 
infection in the vast majority of cases. We are less certain concerning 
the modes of entrance into the body, although it is presumed that the 
virus also enters by the mouth and nose; however, we lack positive 
information upon this point. 

MaAT ^ showed in 1852 by experiments on the human subject that 
the buccal and nasal secretions were infective. Recently Anderson and 
Goldljerger ^ have demonstrated by experiments upon monkeys that 
the nasal and buccal secretions of uncomplicated cases of measles may 
be at times, but are not always, infective. Hektoen * in 1905, as well 
as Goldberger and Anderson, 1911, demonstrated that the virus of 
measles is also contained in the circulating blood. The virus appears 
in the blood at least 24 hours before the eruption appears, and begins 
to diminish about 25 hours after the first appearance of the eruption. 

It has long been assumed that the virus of measles is carried in 
the fine bran-like desquamating epithelium, which is one of the char- 
acteristics of the disease. Mayr long ago failed in his attempts to in- 

' J. A. M. A., Vol. LYII, Xo. 12, Sept. 16, 1911, p. 971. 

' Mavr, Franz: Zeitschr. d. Jc. k. Gesellsch. de Aertze zu Wien, 1852, I, 13-14. 

» J. A. M. A., Vol. LYII, Nov. 11, 1911, p. 1612. 

* Experimental Measles : Jour. Infect. Dis., 1905, Vol. II, p. 238. 


oculate children witli measles by using the desquamating epithelium. 
Anderson and Goldberger also obtained absolutely negative results in 
three experiments, in which it was shown that the "scales" were not 
infective for monkeys. These authorities believe that it is highly prob- 
able, if not altogether certain, that the desquamating epithelium of 
measles in itself does not carry the virus of the disease. This conclu- 
sion is warranted hj epidemiological evidence. 

Measles is so readily communicable that clinicians receive the im- 
pression that the virus is "volatile." It has long been suspected that 
the virus is contained in the expired breath, but this is very doubtful. 
In fact, it may now be stated with confidence that measles is not air- 
borne, in the sense in which this term is usually understood. In any 
case, the radius of danger through the air is confined to the immediate 
surroundings of the patient — that is, within the danger zone of droplet 
infection. Droplet infection is quite possible, as the virus is contained in 
the secretions of the mouth and nose ; furthermore, it evidently requires 
an exceedingly minute quantity of the virus to reproduce the disease in 
man, who is exquisitely susceptible to this infection. 

Chapin has collected important evidence indicating that the infec- 
tion of measles is not air-borne. Thus, in the Pasteur Hospital, Paris, 
each patient is cared for in a separate room opening into a common 
hall. Trained nurses exercise strict medical asepsis. In 2% years after 
this hospital was opened in 1900 many cases of smallpox, diiDhtheria, 
scarlet fever, and 126 cases of measles were cared for. In no instance 
did measles spread within the hospital. xA.t the Children's Hospital in 
Paris (Hopital des Infants Malades), instead of being in separate 
rooms, the beds are separated only by partitions. Strict asepsis is ob- 
served. Of 5,017 cases there were only 7 cross-infections, 6 of measles 
and 1 of diphtheria. Dr. Moizard thinks that this experience proves 
that even measles is not air-borne, for the few cases of this disease 
which did arise were not all in cubicles adjoining those occupied by 
measles patients. Grancher in another Paris hospital had two wards 
in which there were no partitions, but only wire screens around 
the beds, simply as a reminder for the nurses. Of 6,511 patients 
treated from 1890-1900, 115 contracted measles, 7 scarlet fever, and 
1 diphtheria. Grancher insists that measles is probably not an 
air-borne disease. Adjacent patients do not necessarily infect one an- 
other. At various English hospitals similar methods have beeen 
tried with success. These various hospital experiences indicate that 
the danger of aerial infection in measles is much less than is generally 

The infection of measles is usually transmitted more or less directly 
from person to person by means of the excretions from the mouth and 
nose, and most often during the early stages of the disease. Measles 


may be transmitted by third persons or by fomites, though such in- 
stances are rather exceptional. 

Prevention. — The suppression of measles is one of the most diffi- 
cult problems we have to face, for the reason that the disease is one 
of the most highly communicable of all infections, and for the further 
reason that it is most contagious during the preeruptive stage. To 
the student of j^reventive medicine the problem of measles is very 
similar to that of smallpox, and the final control will probably have 
to await a specific prophylactic measure. Improved sanitation, better 
hygiene, and the general advance of civilization, which have made such 
a marked impression upon typhus fever, relapsing fever, typhoid fever, 
and other "filth" diseases, have no influence whatever upon such infec- 
tions as measles or smallpox. 

Measles is such a common disease that parents are prone to take 
little pains to avoid the infection; they even sometimes purposely ex- 
pose their children. This is a mistaken attitude. Special care should 
be exercised especially during the first five years of life, as over 90 
per cent, of the fatal cases occur in this period. While it may be al- 
most hopeless to lessen the morbidity in measles, it is quite possible 
to materially decrease the mortality by simply delaying the age inci- 

Clinical experience plainly indicates that few people die of measles 
if properly cared for. The mortality may, therefore, be decreased by 
careful nursing and protection, especially from pneumonia, which is 
one of the most dangerous complications. Newman sums up the mat- 
ter of prophylaxis when he states that "the prevention and control of 
measles, like that of whooping-cough and tuberculosis, is largely in the 
hands of the public themselves." 

In the present state of our knowledge the prophylaxis of measles 
rests almost entirely upon one measure — isolation. Chapin believes 
that isolation has been a failure in measles. This is because of the 
unrecognized but infectious preeruptive stage. "No amount of isolation 
after the disease is recognized can atone for the harm done before the 
diagnosis is made." Isolation, however, accomplishes one worthy ob- 
ject, viz., the prevention of further damage. Isolation, as carried out 
in our large cities, has had no apparent efEect upon the prevalence of 
the disease. In Aberdeen restrictive measures apparently protected 
only 7 to 10 per cent, of the population. 

Despite its limitations, isolation is quite worth while. Cases should 
be at once reported to the health officer, the house placarded, and visit- 
ing prohibited. Quarantine should not be raised nor should the child 
be permitted to return to school until the manifestations of the disease 
have disappeared. Measles may be treated in the household, but it is 
difficult under ordinary circumstances to prevent the spread of the dis- 


ease to tlie other children. If the case is treated at home, the children 
who have not had the disease should be sent away. 

Mild atypical and unrecognized cases of measles occur, but are far 
less numerous than such cases in scarlet fever, diphtheria, and typhoid. 
Clinical evidence points to the fact that "carriers" of measles are not 
common. The disease is usually spread directly from person to person, 
occasionally indirectly through a third person, or by fomites. Physi- 
cians may convey the infection to healthy children. I am convinced 
that I carried the disease to my own son. When measles is conveyed 
by a third person or by fomites it is by means of contamination with 
the fresh buccal, nasal, or bronchial secretions upon the hands, hand- 
kerchief, or some other object that comes in contact with the mouth or 
nostrils of a susceptible child. Physicians may readily avoid this dan- 
ger by wearing a gown and carefully washing the hands, face, and 
hair, and waiting a reasonable time before visiting healthy children. 

Terminal disinfection is of comparatively little value in preventing 
the spread of measles. After the patient is released from isolation a 
general disinfection with formaldehyde may be practiced, especially if 
healthy children are soon to occupy the playroom or bedroom. How- 
ever, if from 2 to 3 weeks have elapsed, there is practically no danger 
in a well-ventilated, sunny, and clean room. All bedding, towels, hand- 
kerchiefs, and other fabrics that have been exposed should be boiled 
or otherwise disinfected. 

The question of closing the schools in order to prevent the spread 
of measles requires consideration. If the school is closed at the begin- 
ning of an outbreak and the disease continues to spread after two weeks, 
little more will be gained in keeping the school closed, for it must then 
be evident that other factors are at work in spreading the infection. 
As the disease is mainly spread in the preemptive stage, it is sufficient 
to examine the children each morning before they enter school for symp- 
toms of a cold, infection of the eyes, running at the nose, cough, sore 
throat, fever, etc. All such cases should be sent home to await further 
developments. If these measures are taken the school may be kept open. 

McVail suggests that when a child develops measles all the children 
exposed may be allowed to continue at school 8 or 10 days, and then 
excluded for a week to ten days, when those who do not develop the dis- 
ease may be allowed to return. This is a rational plan used in certain 
districts in England. When measles breaks out in an orphan asylum, a 
public institution, or an encampment, the only chance of checking the 
spread of the disease is through the early recognition of first symptoms 
and isolation. 



Scarlet fever is an acute febrile infection characterized by a diffuse 
eruption which ai)i)ears during the first day or two of the fever, and 
sore throat of variable intensity. The seasonal prevalence of scarlet 
fever resembles that of diphtheria. The disease increases in the fall 
of tlie year, due, in part, to the gathering of children in the schools. 
The period of incubation is from 1 to 7 days; usually 3 to 4. In a 
few instances, in which individuals have been inoculated with the blood 
of scarlet fever patients, 3 to 4 days elapsed before the onset of symp- 
toms. Scarlet fever is rare in the tropics; when introduced it soon 
dies out. There is probably always more or less scarlet fever in any 
thickly settled district in the temperate zone. The infection is kept 
alive largely through the mild and unrecognized cases. Scarlet fever 
varies greatly in intensity in different outbreaks. In some epidemics 
the death rate is 30 per cent.; in others it is practically nil. 

Landsteiner, Levaditi and Prasek ^ apparently succeeded in transfer- 
ring scarlet fever to chimpanzees and also to monkeys. The animals 
were inoculated both by ai)plying throat swabs from scarlet fever patients 
to the pharynx of the animals, and also by injecting the animals with 
blood from scarlet fever patients. While the nature of the virus is still 
unknown, it seems to be present in the tonsils, tongue, blood, lymph 
nodes, and pericardial fluid. 

The cause of scarlet fever is not known. Streptococci are almost 
constantly found in the throat and blood of scarlet fever cases. Klein 
in 1885 was the first to advocate the Streptococcus scarlatina; as the 
specific cause of scarlet fever. Kurth assigns an etiological factor to 
the "Streptococcus conglomeratus." It is said to produce a rash in 
animals and men who are injected with it. The chief reasons for con- 
sidering streptococci as the cause of scarlet fever are that they are con- 
stantly found in the throat of scarlet fever patients; that frequently 
they can be isolated from the blood of scarlet fever patients during life, 
and almost constantly after death; the cause of the complications and 
death in the majority of cases of scarlet fever is due to the strepto- 
coccus. It is probable, however, that the streptococcus plays a secondary 
role in scarlet fever as it does in smallpox; the disease itself may be 
due to a protozoon-like body described by ilallory, which lowers the 
resistance of the organism to streptococcal invasion. 

Modes of Transmission. — It is taken for granted that the virus of 
scarlet fever is contained in the secretions from the nose, throat, and 
respiratory tract. The virus probably enters by the mouth and respira- 
tory passages. Scarlet fever is not contagious during the period of 

^ Annales de I'lnst. Pasteur, Oct., 1911, XXV, No. 10, p. 754. 


incubation; little, if any, during the period of invasion. It is most 
contagious during the jDeriod of eruption. Scarlet fever is readily 
communicable, but less so than measles or smallpox ; it ranks about with 

It has long been accepted and taught by the medical profession 
that the desquamation is the most infectious stage of scarlet fever, 
and it is now very difficult to unteach the public this erroneous view. 
It is now known that desquamating patients may, as a rule, be safely 
released from quarantine in the 6th week of their attack of scarlet 
fever, provided they have no mucous complications or other sequelae. 
Convalescents may be a source of danger to others even after desquama- 
tion has ceased. This fact has been emj^hasized from a study of the 
so-called "return cases." Thus convalescents are released from hos- 
pital and permitted to return home; soon another case appears in one 
of the members of the household, who in turn comes to the hospital. 
Neech in a study of 15,000 cases found that the percentage of return 
cases was 1.86 in those cases who submitted to an average period of 
isolation of -±9 da3's or under. With an average period of 50 to 56 
days the percentage was 1.12; where the isolation extended to between 
57 and 65 da3's the percentage of return cases was 1. McCullom states 
that in the South Department of the City Hospital, Boston, the chil- 
dren are kept 50 days, and no patient is released who has a discharge 
from the nose or an abnormal condition of the throat. Of 3,000 pa- 
tients discharged from the scarlet fever ward, 1.7 per cent, of return 
eases occurred. McCullom is inclined to regard the infection as com- 
ing from mild and unrecognized cases of the disease rather than from 
the discharged case. 

There is no accurate means of determining just how long a child 
remains infective after scarlet fever. The period of detention varies 
very much. Fifty days may be taken as a safe average. In 'New Ha- 
ven and Seattle cases are dismissed after desquamation; in North 
Dakota 5 days after desquamation; in Ohio and South Dakota 10 days 
after desquamation. In various cities and states the period of isola- 
tion varies from 3 weeks to 8 weeks unless the physician certifies that 
desquamation has ceased. In Milwaukee, Paterson, and Pittsburg it 
is never maintained longer than 30 days, even if desquamation con- 
tinues. Owing to our lack of knowledge on the subject, the period 
of isolation must remain more or less guesswork. An unduly long 
detention is a hardship upon the patient and the family; on the other 
hand, a scant period is hazardous to the community. Cases with rhinor- 
rhea, otorrhea, throat trouble, or discharging abscesses must receive spe- 
cial care, as the secretions from these parts are now known to remain 
infective for a long time. 

Many cases of walking scarlet fever present little further evidence 


than a passing sore throat. These cases doubtless spread the disease, 
especially in schools. Third persons may carry the disease perhaps on 
their clothing and perhaps also as carriers. Toys, cups, spoons, ther- 
mometers, handkerchiefs, and other oljjects contaminated by the secre- 
tions of tlie mouth j)lay tlie same role here that they do in diphtheria. 
Scarlet fever is not air-borne; at least the radius of infection is limited 
to droplet infection. 

MiLK-BOHNE Scarlet Fever. — Milk is a rather frequent vehicle for 
scarlet fever infection. The milk is practically always contaminated 
from human sources. There is, however, some suspicion that strepto- 
coccal diseases of the cow may in some instances be identical with scarlet 
fever. This is doubtful. It is known, however, that such diseases of the 
udders of the cows may cause outbreaks of an infection resembling 
scarlet fever. Trask collected 51 scarlet fever epidemics reported as 
spread by milk. Twenty-five of tliese occurred in the United States and 
26 in Great Britain. In 35 of the epidemics a case of scarlet fever was 
found at the producing farm, the distributing dairy, or milkshop at such 
a time as to have been the possible source of infection; in 3 of tlie out- 
breaks the bottles returned from infected households and refilled without 
previous sterilization were given as the source of infection; in 3 of the 
outbreaks scarlet fever persons handled the milk or milk utensils, and 
in 12 of the outbreaks the cows were milked by persons having scarlet 
fever; in one epidemic the same person nursed the sick and handled the 
milk; in 2 of the outbreaks the source of infection was supposed to be 
due to disease of the cow. A milk-borne outbreak in Washington was 
traced to a convalescent with a discharging ulcer on the finger. Milk- 
borne outbreaks of scarlet fever are sometimes very extensive. 

An unusually extensive milk-borne outbreak of scarlet fever occurred 
in Boston during April and May, 1910. A total of 842 cases were 
reported from Boston and the surrounding towns of Chelsea, Winthrop, 
Cambridge, Somerville, ]\Ialden, and Everett. Investigation showed 
that most of the cases occurred on the route of a large milk contractor. 
Of the 409 cases in Boston, 2SG, or nearly 70 per cent., were on the 
route of this dealer; while 123, or 30 ])er cent., used other milk. Of 
the 155 cases that occurred in Cambridge, 126, or over 80 per cent., 
were on the route of the same dealer. About the same proportion of 
the cases in the other cities used the milk of this dealer. The cases 
appeared suddenly April 25th, and the outbreak ceased May 7th. The 
epidemic reached its highest mark on April 29th, when 128 cases were 
reported. The indications were plain that the outbreak was the result 
of more than a single infection. The milk was pasteurized at 60° C. 
for 30 minutes on April 27th, and three days following there was a 
notable and sharp decline in the number of cases. The source of the 
infection could not be traced, although it probably consisted of a 


"missed" case oii one of the 250 dairy farms from which the dealer ob- 
tained this particular supply of milk. 

Immunity. — One attack of scarlet fever usually protects against 
subsequent attacks. In rare instances second attacks may occur after 
an interval of several years. Children under 10 are most susceptible. 
Sucklings .are rarely attacked, though susceptible. After the 10th year 
the resistance to the disease increases. Ninety per cent, of the fatal 
eases occur in children under 10 years old. The reason why infants at 
the breast are less likely to take the disease may be on account of the 
diminished chances of the infection entering the mouth. The immunity 
acquired in later life may in part be due to previous unrecognized mild 

Prophylaxis. — Prophylaxis in scarlet fever must necessarily be in 
excess of the requirements, awaiting more precise knowledge of its 
cause and modes of transmission. The essential features of prevention 
consist in isolation and disinfection. It is important to recognize the 
mild cases in schools through an efficient medical inspection. The 
answer to the question whether schools should be closed when scarlet 
fever breaks out varies with the circumstances. In country districts 
this is advisable, as the children may be kept separate, but in the cities 
little is gained. There is no objection to treating a case of scarlet fever 
in the household, provided a suitable room and trained attendant may be 
had. The infection may be confined to the sick room, but it is preferable 
to take no chances and send the susceptible individuals out of the 
house. The nurse should use the precautions described for dijDhtheria, 
smallpox, or measles. The physician should wear a gown and thor- 
oughly disinfect his hands and other exposed parts after the visit. Spe- 
cial care must be taken with the thermometer and other instruments. 
The physician may find the necessary precautions and disinfection to 
be irksome, but they should not be shirked in Justice to his other pa- 
tients and the community. 

The discharges from the mouth, nose, and respiratory passages, 
etc., should be collected upon suitable fabrics and burned. Bed and 
body clothing, dishes, and other exposed objects must be disinfected. 
Care must be taken concerning remnants of food from the sick room. 
Scarlet fever is not as highly contagious as measles, but the meas- 
ures employed should be practically the same until at least we have 
more definite knowledge concerning the channels of entrance and exit 
of the virus and its modes of transmission. The virus of scarlet fever 
is more resistant than that of measles. It clings persistently to cloth- 
ing and various objects. A terminal disinfection with formaldehyde gas 
may be practiced^ although little seems to be gained thereby. A thorough 
cleansing of all surfaces, with a good sunning and airing of the room, is 
always in order. All fabrics and other objects that have been exposed 


should be disinfected. Tlie virus is killed with agents tliat destroy 
non-spore-bearing l)acteri;i. In Glasgow a sanitary wash-house has been 
established, where the clothing of scarlet fever cases may be disin- 
fected and washed. This is a commendable example that might be fol- 
lowed with advantage by other cities. 

Specific Prophylaxis. — Gabritschewsky first proposed the use of 
streptococcus vaccines as a propliylaxis against scarlet fever. He used a 
concentrated bouillon culture of the streptococcus isolated from a person 
ill with scarlet fever. The culture is killed by heating to 60° C, and 0.5 
per cent, carbolic acid added. Gabritschewsky uses 0.5 c. c. of the concen- 
trated bouillon culture in children 2 to 10 years old. For those younger 
half this amount, and adults twice this amount, is used. The injec- 
tions are given subcutaneously in the abdomen, thigh, back, or arm. 
Another method of dosage is to use 0.1 c. c. for each year of the 
child's age with 0.25 c. c. as the minimum and 1 c. c. as the maximum. 
Three doses are given in periods of 7 or 10 days, the dosage increasing 
at each injection li/^ to 2 times the previous dose. 

The only cases in which the vaccines are withheld are: (1) in those 
having a high temperature, although even these have received the 
prophylactic without evident untoward results; (2) in very young in- 
fants or patients who, from some cause or other, are greatly exhausted; 
and (3) in those having nephritis. 

The claim is made that after 3 injections of the vaccine, and usu- 
ally after 2, a complete immunity is established against scarlet fever. 
The immunity does not appear until 5 to 7 days after the last dose. 
The duration and degree of the immunity is problematical, as the vac- 
cines have been in use so short a time. It appears that the immunity 
probably remaias at least lYo years. 

The usual reactions, both local and general, follow these injections, 
but in 10-15 per cent, of the persons injected quite a different reaction 
occurs. Twenty-four hours after the injection there appears on the 
chest and abdomen, sometimes extending over the rest of the body, a 
punctate erythema very much like the eruption of scarlet fever, but not 
followed by any desquamation. The eruption lasts 1-3 days, and may 
be accompanied by sore throat, some swelling of the lymph glands, 
and often a so-called strawberry tongue. Rarely a rather severe 
reaction with high fever, a little albumin in the urine, and 
marked prostration occurs, but it rapidly disappears without permanent 

The reactions following the second injection are usually much less 
than after the first; often none at all; and after the third injection 
there are rarely any unpleasant features. The longer the intervals be- 
tween the injections the more frequently will there be a reaction to the 
second and third injections. The interval of a week is considered the 


most satisfactory. Richard M. Smith ^ has collected over 50,000 in- 
stances in which the killed streptococcus cultures have been injected 
with only 1 fatality, which was a child 23/2 years old who had a severe 
nephritis and died on the third day after the injection. 

The method has been extensively tried in Russia with favorable re- 
sults, so far as one may judge from the published reports. Thus Smir- 
noff used the vaccines in 13 small communities in Russia where the 
sanitary conditions were very poor and the conditions favorable for the 
spread of scarlet fever. In one village there were 34 unvaccinated 
children, of whom 24, or 70.6 per cent., had scarlet fever; 48 vacci- 
nated children, of whom 4, or 8.3 per cent., had scarlet fever. Of 
these 4, 3 came down within a week after the first inoculation, the 
other one 5 days after the second inoculation, too soon for immunity 
to have been established. The results in the other villages were equally 
or more satisfactory. Thus, all told, Smirnoff vaccinated 455 cases, 
only a part of whom allowed second injections. The results are as 
follows : 

1 injection. — 285 cases — 5 cases of scarlet fever 

2 " —148 " —2 " " " « 

3 « _ 22 " —no " " " « 

Of the 7 cases of scarlet fever 3 were within 7 days of first vac- 
cination, 2 were within 7 days of second vaccination. 

In the villages without vaccination 20 per cent, contracted scarlet 
fever and 11.1 per cent. died. In villages with vaccination 3.7 per 
cent, contracted scarlet fever, none died. 

Yemelyanoff used the prophylactic in an epidemic in Krakow in 
which there were 8 or 10 new cases reported every day. Six hundred 
and ten persons were inoculated; of these not a single one contracted 
the disease. Often it was possible to keep the schools open in certain 
districts where inoculations were used, even though the children came 
from infected houses. 

Equally good results are reported by a number of other Russian 
observers. It therefore seems that in the streptococcus vaccines we 
have a useful means to control epidemics of scarlet fever. Their use, 
with proper care, is attended with no harmful results, and they de- 
serve a wider trial in this country. 

Moser's polyvalent antistreptococcus serum has been used in the 
treatment of the disease, but has not been advocated as a prophylactic. 

^Boston Medical and Surgical Journal, CLXII, 8, p. 242, Feb. 24, 1910. 




Whooping-cough occurs in epidemics, which vary greatly in viru- 
lence, intensity, and mortality. The disease is more frequent and se- 
vere in cold climates; otherwise uninfluenced by season and weather. 
The cause of whooping-cough is a small bacillus, described by Bordet 
and Gengou.^ This bacillus is found most readily in the beginning of 
the disease, in that part of the expectoration which comes from the 
region in which the bacteria are most active; that is, in the products 
from the depths of the bronchi brought up during the paroxysms. In 
this exudate, which is white, thick, and rich in leukocytes, the bacilli 
exist in considerable numbers and sometimes in almost pure culture. 

liode of Transmission. — Whooping-cough is usually transmitted di- 
rectly from person to person in the same ways that diphtheria and other 
infections contained in the secretions of the mouth and nose are spread; 
it is less frequently transmitted by indirect contact or by third persons. 
Handkerchiefs, toys, drinking cups, roller towels, and other objects 
recently contaminated with the infective secretions may act as directors. 
It may also be transmitted by droplet infection, although in the ordinary 
sense whooping-cough is not air-borne. 

Jahn and others called attention to the fact that domestic animals 
may be affected by whooping-cough, and that they may be the means of 
transmitting it to children. It is most frequently observed in dogs, but 
has also been noted in cats. Whooping-cough may be reproduced in 
puppies by dropping a pure culture into the nares; once started, it is 
readily transmitted from puppy to puppy. Klimenco - and Fraenkel ^ 
were able to produce what seemed like typical pertussis in monkeys, and 
Inabo * showed that injection of the bacillus in an ape gave rise to a 
typical whooping-cough with an incubation period of 13 days. ]\Iallory 
and Horner ° have shown that the bacilli are found in masses in the 
superficial layer of the trachea, thereby mechanically parah'zing the 

Whooping-cough is apparently not contagious during the period of in- 
cubation, but is communicable from the appearance of the early symp- 
toms, and is most contagious during the early stage. It may be trans- 
mitted in the late stages and after convalescence. Wliile the virus is 
known to be in the secretions from the respiratory tract, all secretions 
from the mouth and nose must be regarded as infective. 

Immunity. — There is no natural immunity to whooping-cough; all 
are susceptible. The greatest susceptibility is between 6 months to 5 

^ Ann. de J'Inst. Pasieur, Vol. XX. 1906, p. 731. 
^ Centralbl f. BakterioJ.. 1908. XLA^II, 64. 
^Munchen. med. Wochschr.. 1908, LY, 1683. 
* Ztschr. f. Kinderh., June 15. 1912. 
^Jour. Med. Ees., Nov., 1912, XXVII, 2, p. 115. 


years. After 5 years the susceptibility decreases with age. One at- 
tack confers a definite and prolonged immunity ; second attacks are rare. 

Prevention. — The incubation is probably 1 to 2 weeks, but the time 
is indefinite, owing to vagueness of the onset of symptoms. If 16 days 
have passed without symptoms the danger may be considered as having 
passed. The long-drawn-out nature of the disease, the difficulty of 
diagnosis in the early stages when it is most contagious, and the fact 
that patients sometimes continue to spread the infection for 6 weeks 
after apparent recovery, make the control of whooping-cough an ex- 
ceedingly difficult problem. Hence, with whooping-cough we have the 
same difficult problem that confronts us in the prevention of measles. 

Whooping-cough should be reported, houses placarded, and the pa- 
tient isolated, but the isolation in this case need not include strict con- 
finement to a room. This, in fact, may be an unnecessary hardship to 
the patient, who does better out of doors. If the patient is permitted 
to take the air, he must avoid contact with his fellowmen and not go 
to school, theater, church, public assemblies, nor ride in street cars or 
public vehicles. Children should go out only when accompanied by an 
intelligent caretaker as a protection to others. It has been suggested 
that children with whooping-cough who are permitted their liberty 
should be plainly labeled with a red cross on their arm, or a yellow 
flag conspicuously displayed on their clothing, to serve as a warning 
to others. 

Patients should not be released from quarantine until the spasmodic 
stage is over. The duration of isolation varies in different cities; thus 
it is 6 weeks in Montclair, X. J. ; on recovery in Providence ; as long 
as the cough lasts in Boston. In Michigan the disease is considered 
infectious 3 weeks before the whoop and -4 to G weeks after apparent 
recovery. The State Board of Health of that state requires disinfec- 
tion of the clothing and premises before the patient is released, and 
forbids public funerals in deaths from whooping-cough. 

Individual prophylaxis consists in avoiding the infection. The great- 
est care in this regard should be taken with children before the age 
of 5 years. Dogs, cats, and other domestic animals should be kept 
away from the patient, and the possibility of conveying the disease in 
this way must be guarded against in the susceptible. 

The control of whooping-cough is a matter which is largely in the 
hands ' of the public itself. The dangerous nature of this infection 
should be emphasized, and people taught that it is contagious both be- 
fore and after the '''whoop." Mild cases which do not have the charac- 
teristic whoop spread the disease; this is especially common in adults. 

Mortality. — The dangerous nature of whooping-cough is not gen- 
erally realized. Thus in Glasgow the annual mortality from whooping- 
cough for 10 years, 1855-1891, was 13.5 per thousand inhabitants, and 


exceeded that from any other acute communicable disease. In Eng- 
land and Wales in 1891 more deaths occurred from whooping-cough 
than from measles, diphtheria, scarlet fever, or typhoid fever. In our 
country the disease ranks high as a cause of death among children. 
The mortality figures would be still higher if all the deaths directly or 
indirectly due to it were completely reported, for the fatal termination 
is usually due to complications and sequelae which occur in one-third 
to one-fourth of all cases. As a result of these complications the origi- 
nal disease is frequently lost sight of entirely in the vital statistics. 
According to Farr's law — that contagious diseases increase as density 
of population increases — the death rate from whooping-cough in our 
country will undoubtedly increase in our more sparsely settled states 
with increasing population and rapidly extending lines of railroad and 
other facilities, and with easy, frequent, and rapid movements of the 


Mumps usually occurs between the ages of 5 to 15 years. There is 
decreased susceptibility both before and after this time. One attack 
usually confers immunity, but second attacks are by no means rare, 
and third attacks are sometimes reported. The disease may occur as 
epidemics in institutions, which usually develop slowly and last a long 
time. Mumps is contagious before the symptoms appear, and for some 
time, even 6 weeks, after symptoms have disappeared. The disease 
is usually spread by direct contact; rarely by indirect contact or by a 
third person. It is not air-borne. The virus is contained in the secre- 
tions from the mouth and perhaps the nose. The incubation is variously 
stated at from 4-25 days; it is usually prolonged. 

Mumps is required to be reported in Maryland, Grand Rapids, and 
Raleigh, and placarded in Cleveland. Prevention dei^ends upon the 
usual practice of isolation and disinfection. 


Lobar pneumonia is a communicable disease which should be classi- 
fied with the infectious fevers. If pneumonia were a new disease it 
would be regarded as "contagious," and its spread would be guarded 
against by isolation and the application of antiseptic principles. Many 
different infections are caused by the pneumococcus, but here we will 
consider only the specific self-limiting disease associated with massive 
involvements of one or more lobes of the lung, known as lobar or croup- 
ous pneumonia. The pneumococcus is found not alone in the local 
lung lesions, but it also invades the blood. 


Pneumonia is one of the most prevalent and fatal of all acute 
diseases. As a cause of death it rivals and sometimes exceeds tuber- 
culosis. According to the U. S. Census of 1890, over 9 per cent, of 
all deaths were due to pneumonia, and in 1900 over 10.5 per cent. 
Pneumonia is probably on the increase, owing to factors favoring the 
spread of the infection and to certain devitalizing influences of modern 
life which heighten susceptibility to the disease; further, more persons 
are now saved from the acute and fatal infections of childhood and adoles- 
cence to become victims of pneumonia later in life. 

Pneumonia occurs everywhere, in all climates, at all times of the 
year, in both sexes, and at all ages; it is more frequent, however, dur- 
ing the cold months of the year. The incidence is marked at both ex- 
tremes of life. It is common in children under six years; between the 
sixth or fifteenth year the predisposition is less marked, but for each 
subsequent decade it increases. 

Pneumonia occurs in well-marked epidemics. Wells gives an ex- 
haustive tabulation of the epidemics of pneumonia extending back to 
1440.^ Epidemics of pneumonia have occurred in all parts of the 
world: in Alaska, at Erlangen, Boston, Ireland, Italy, France, Switzer- 
land, and on board ships. The disease has also been observed to spread 
in hospitals and in houses. Epidemics of pneumonia probably only 
occur when the organism attains an increased virulence and the factors 
for its dissemination are favorable. It is quite proper to regard pneu- 
monia as pandemic. 

Modes of Transmission. — The pneumococcus leaves the mouth main- 
ly in the discharges from the mouth and nose, and enters the system 
through the same channels. The infection is spread directly and in- 
directly through the great variety of ways discussed under diphtheria 
and tuberculosis. Indirect transmission through cups, thermometers, 
handkerchiefs, and other objects contaminated with the fresh discharges 
occurs; and droplet infection also comes into consideration. 

Resistance of the Virus. — The pneumococcus is a frail organism; 
it does not multiply in nature outside of the body and indirect trans- 
mission is not likely except with fresh infectious material. Even upon 
artificial culture media the life of the pneumococcus is brief; it must 
be transplanted every 2 or 3 days in order to keep it alive; it is cus- 
tomary in laboratories to pass it through a susceptible animal, such as 
a mouse or rabbit, from time to time, in order to maintain its viru- 

The pneumococcus is readily destroyed by heat; 52° C. for 10 min- 
utes is sufficient. On the other hand, it withstands low temperatures 
very well. The ordinary germicidal agents destroy it quickly and with 

V. A. M. A., Feb. 23, 1889. Med. News, Maj 20, 1905, 


certainly. It may live lor moiitlis in dried sputum, in wliicli it also 
maintains its virulence. 

Immunity. — One attack of pneumonia does not leave an immunity. 
In I act. one attack ])redisi)oses to subsequent attacks, as is the case with 
erysipelas and rlicuiiiatic fever. Man, however, must possess a certain 
degree of resistance to the ])neumococcus, else the disease would he 
even more prevalent than it is, and recovery less frequent. 

The mechanism of the immunity to this infection is not at all un- 
derstood. Phagocytosis may play a jirominent, perhaps a dominant, 
role. Protective antibodies, rather feeble, have hcen found in the blood 
serum of immunized animals, and- also in the blood scrum of persons 
who have recovered from pneumonia. The pneumococcic attack, espe- 
cially the crisis, resembles an anaphylactic reaction, and, while the 
mechanism of immunity in this infection is probably complex, the best 
explanation of it at present is in terms of anaphylaxis. 

Many weakening diseases diminish resistance to the pneumococcus. 
Pneumonia is frequent in alcoholics, and is commonly brought on by 
exposure to cold, to trauma, or to local irritation. It is a frequent 
complication of typhoid fever, influenza, Bright's disease, and other 
debilitating affections. Old age, as well as other enfeebling conditions, 
may act as a predisposing cause by lowering immunity. Other factors 
which predispose to pneumonia are sudden changes in temperature, irri- 
tation caused by aspiration of foreign substances, or the inhalation of 
dust or irritating vapors. 

It should be remembered that pneumonia, like other communicable 
infections, frequently attacks the strong and robust. 

Prevention. — The prevention of pneumonia must be based upon gen- 
eral principles guided by analogy from analogous infections. As long 
as we are ignorant of the fundamental factors concerned in the etiology 
and pathogenesis of the disease, our preventive measures must lack 

The virulent pneumococcus should not be lightly regarded as a nor- 
mal inhabitant of the mouth, throat, and nose. Because the pneumo- 
coccus is very widely spread and the disease is ubiquitous, and because 
the associated factors which determine infection seem complicated and 
not well understood, are not sufficient excuses for a supine and hope- 
less attitude. The problem of tuberculosis has been attacked with vigor 
with scarcely better understanding of the fundamental problems at 
issue. Each case of pneumonia should be regarded as a focus for the 
spread of the infection. Ultimate control of the disease will probably 
have to await the discovery of a specific prophylactic and the recognition 
of dangerous carriers. Meanwhile we should think of pneumonia very 
much as we think of whooping-cough and influenza, as an infection 
which is spread from man to man through the secretions of the mouth 


and nose. It is true that the pnemnococcus is frequently found in the 
buccal secretions of healthy persons. Sternberg in 1880 first demon- 
strated the pneumococcus in his own saliva. Netter found it in 20 
per cent, of the persons whom he examined, and the New York Com- 
mission reported its presence in from 48 to 85 per cent. Pneumococci 
have been isolated from the throat in 50 out of 80 normal individuals, 
from 66 out of 74 cases of lobar and lobular pneumonia, from 10 out 
of 15 "common colds," and from 14 out of 31 cases of miscellaneous 
diseases; in other words, many persons are pneumococcus carriers. 
However, there are many different strains of the pneumococcus, which 
vary greatly in pathogenic power. We therefore do not know how 
many of these pneumococcus carriers are dangerous to the host and 
also to his fellowmen. A somewhat analogous situation is noted in the 
diphtheria-like organisms in the throats of about 1 per cent, of all healthy 
individuals. It is probable that the virulence of the pneumococcus is 
higher in pneumonia than in the above-mentioned carriers, although 
this is a very difficult matter to determine. The findings of the Medi- 
cal Commission for the Investigation of Acute Eespiratory Diseases 
seem to make prevention a less hopeless task than at first sight ap- 
pears possible from the widespread distribution of the pneumococcus. 
It was shown that, while a number of individuals constantly harbor 
virulent strains of the pneumococci in their mouths, the majority of 
people do so only from time to time. Individuals who come in con- 
tact with pneumonia patients are more apt to harbor the pneumococ- 
cus than those not so exposed. Patients convalescent from pneumonia 
may carry virulent organisms in their respiratory passages for weeks 
or even months. 

Pneumonia should be added to the list of diseases requiring com- 
pulsory notification. Cases should be isolated at least in the same sense 
that tuberculosis is isolated — the discharges from the nose and throat 
should be burned or disinfected. If the patient is treated at home, the 
house should be placarded in order to discourage visiting and as an 
educational measure. 

There is no specific prophylaxis for pneumonia. Prevention con- 
sists in avoiding the infection, sustaining the tone of the machine, 
care and cleanliness of the upper respiratory passages, avoiding chills, 
exposure, and other predisposing causes, and especially avoiding living 
in stuffy, ill-ventilated rooms and dusty atmospheres. 

As carriers doubtless play an important role in disseminating this 
infection, the education of the public concerning certain sanitary habits 
should be actively continued. These include the danger of spitting 
promiscuously and of kissing; the proper care to be exercised in sneez- 
ing and coughing; the peril in the common drinking cup, the roller 
towel; and the habit of placing unnecessary things in the mouth. 


It should become common knowledge that anything which tends to 
reduce vitality predisposes to pneumonia, such as dissipation, loss of 
sleep, overwork, worry, poor or insufficient food, lack of exercise, al- 
cohol, colds, or excesses of all kinds; the atonic effect of living in 
overheated rooms, and the injurious effect of excessively dried and 
warmed air, and sleeping in Avarmcd rooms. Cold baths, regulation of 
temperature and ventilation, sleeping with open windows or in the open 
air, are useful prophylactic measures for pneumonia as well as tuber- 
culosis, "colds," and a large group of diseases. 

Upon the Isthmus of Panama pneumonia was unduly prevalent 
owing to the habit of the perspiring workmen sleeping exposed to the 
trade winds. According to Carter, this was largely controlled by sup- 
plying the men with blankets. In Chicago, Evans believes that the 
prevalence of pneumonia was influenced by better ventilation of the 
street cars. Allaying street dust and house dust removes one of the 
predisposing causes of pneumonia and other respiratory infections. 

Health officers may assist in the cause by disseminating knowledge 
concerning the disease and by enforcing antispitting regulations, by 
proper cleansing and oiling of streets, by requiring a stricter compli- 
ance with building and housing laws, and by the regulation of the ven- 
tilation and conditions of the air in theaters, schools, street cars, and 
public buildings. 


The cause of influenza is assumed to be a small bacillus which is 
constantly associated with the disease; it was described by Pfeiffer in 
1892 and 1893.^ Influenza prevails without relation to climate, wind, 
weather, or telluric conditions. It occurs sporadically, in epidemics 
and in great pandemics. In 1889 and 1890 influenza spread to the 
four quarters of the globe, and, judged by the morbidity and mortality, 
this was the most extensive and serious pandemic that has occurred in 
modern times. These worldwide outbreaks usually spread from east 
to west. 

Immunity. — 'Immunity to influenza is slight; in fact, one attack 
seems to predispose to subsequent attacks; second and third attacks are 
common as a result of new infections or reinfections. Influenza bacil- 
lus carriers are numerous. Males and the robust individuals in a com- 
munity seem more susceptible, perhaps on account of greater expo- 

Modes of Transmission. — Influenza is spread directly from person 
to person. It is highly contagious in the early stages. The influenza 
bacillus is found in the secretions from the nose, throat, and respira- 

^Deutsch. med. Wochenschr., 2, 1892, p. 28. Zeitschr. f. Byg., XIII, 1893. 


tory tract. The bacillus does not multiply outside the body and has 
a very feeble resistance. It grows with difficulty upon artificial cul- 
ture media and soon dies out; therefore "contact" infection or the use 
of handkercliiefs, towels, cups, and other objects contaminated with 
the fresh secretions are the common modes of transmission. Influenza 
is kept alive in interepidemic years in carriers. Lord found the bacil- 
lus influenza in 25 to 59 per cent, of all cases with cough and expectora- 
tion in an interepidemic period in Boston. 

Prophylaxis. — Prophylaxis is practically the same as for all other 
infections transferred by the secretions from the mouth and nose. Iso- 
lation is not always practicable, but patients for their own good as well 
as the protection of others should remain in bed during the febrile 
stage. This one measure would very largely diminish the prevalence of 
influenza as well as common colds. The infection could be kept out of 
a country by strict maritime quarantine, provided mild cases and car- 
riers could be recognized; this, however, is not practicable. The pub- 
lic has not sufficient regard for influenza to .tolerate aggressive meas- 
ures. The disease may frequently be avoided by individual prophy- 
laxis. During epidemics individuals should avoid theaters, mass meet- 
ings, closed and crowded cars, and close contact with their fellowmen, 
especially those who have catarrhal symptoms. It is quite worth while 
to isolate the first case of influenza in a household in order to prevent 
a house epidemic. This may be done on precisely parallel lines to those 
described for diphtheria. Influenza is especially dangerous when com- 
plicating pulmonary tuberculosis, and care should be taken to keep it 
out of sanitaria. Even during epidemics influenza may successfully 
be kept out of institutions by an intelligent quarantine. Once within 
the walls, it is exceedingly difficult to control. Persons who continually 
carry the influenza bacillus in their nose, throat, or respiratory tract 
should guard against exposure to wet and cold on account of the dan- 
ger of reinfection. Influenza is another one of those diseases the con- 
trol of which rests with the public. Education, therefore, is of prime 
importance. The danger from the use of the common drinking cup, 
the roller towel, kissing, droplet infection, handkerchiefs, pipes, toys, 
soda-water glasses, spoons, and other objects recently mouthed should 
be emphasized; spitting ordinances enforced, ventilation and overcrowd- 
ing of street cars corrected, and dust allayed. 


More people probably suffer from common colds than from any other 
single ailment. Vital statistics give no hint of the prevalence and im- 
portance of these minor affections because the mortality is nil and the 
morbidity records are notoriously imperfect and difficult to collect. Could 


the sum total of suffering, inconveniences, sequelae, and economic loss 
resulting from common colds be obtained, it would at once promote 
these infections from the trivial into the rank of tlie serious diseases. 

The common colds here considered are a group of acute infections 
of the mucous membranes of the nose, pharynx, tonsils, larynx, trachea, 
or larger bronchi. A common cold is not merely a congestion, it is 
an infection. 

Congestion and inflammation of the mucous membrane of the up- 
per respiratory tract frequently occur as a result of irritants other 
than bacteria. Thus, chemical and mechanical irritants will produce a 
congestion or inflammation; an increased acidity causes a flaring up of 
the mucous membranes, especially of the nose ; and many other local 
and reflex causes lead to acute or chronic catarrhal conditions of these 
membranes, which may become exquisitely sensitive and sometimes 
hypersusceptible. In the absence of the proper bacteria, however, these 
conditions do not develop into infectious colds, and are, therefore, not 

The popular fallacy of colds being due to exposure to drafts, sud- 
den changes of temperature, and chilling of the body clings persistently 
in both the professional and lay mind. These are predisposing causes 
and will not produce a cold without the presence of the specific cause. 
The bacteria usually found associated with these catarrhal infections 
are : staphylococci, streptococci, pneumococci, influenza bacillus, the 
BaciUus catarrhalis, and other bacteria. The etiological relationship 
between these organisms and the disease is not always clear. Many 
of the above-mentioned bacteria are also found normally upon the 
mucous membranes of the nose, mouth, throat, and upper resj)iratory 
passages; reinfections must, therefore, be common, and predisposing 
factors which diminish resistance have a special importance. Common 
colds frequently attack the strong and robust if exposed. 

Colds are contracted from other persons having colds, just as diph- 
theria is contracted from diphtheria. Arctic explorers exposed to all 
the conditions ordinarily supposed to produce colds do not suffer from 
these ailments until they return to civilization and become reinfected 
by contact with their fellowmen. A campaign to prevent the spread 
of the common cold would have much collateral good in aiding the 
suppression of tuberculosis and causing a diminution of pneumonia and 
other infections. Common colds occur in epidemics and have all the 
earmarks of a contagious disease. Colds are apt to go through all the 
members of a household, and outbreaks in schools, factories, and other 
places where people are closely associated frequently occur and result 
in considerable loss of time and money. 

^^^lile common colds are never fatal, the complications and sequelae 
jire serious. These are : rheumatic fever, pneumonia, sinusitis, nephritis, 


and a depressed vitality which favors other infections and hastens the 
progress of organic diseases. 

Common colds are perhaps most contagions during the early stages. 
If persons would isolate themselves by remaining in bed during the 
first three days of a cold, they would not only benefit themselves, but 
would largely prevent the spread of the infection. The contagiousness 
and severity of colds vary greatly in different epidemics and in dif- 
ferent seasons of the year, depending upon the particular microorgan- 
ism involved and other factors not well imderstood. 

Prevention. — The prevention of colds consists, first, in avoiding the 
infection, and, secondly, in guarding against the predisposing causes. 
Contact should be avoided with persons who have colds, especially in 
street cars, offices, and other poorly ventilated spaces where the risk of 
persons coughing or sneezing directly in one's face is imminent. Con- 
tact with the infection may further be guarded against by a careful 
self-education in sanitary habits and cleanliness based Upon the mod- 
ern conception of contact infection. Colds, like other diseases con- 
veyed in the secretions from the nose and mouth, are often conveyed by 
direct and indirect contact through lack of hygienic cleanliness and 
a disregard of sanitary habits. Kissing, the common drinking cup, 
the roller towel, pipes, toys, pencils, fingers, food, and other objects 
contaminated with the fresh secretions will transmit the disease. 

The predisposing causes of colds include a number of conditions 
that depress vitality and thereby diminish resistance. The mechanism 
by which immunity is lessened has been discussed on page 351. The 
principal predisposing factors in catching cold are : vitiated air, dust, 
drafts, sudden changes of temperature, exposure to cold and wet, over- 
work, loss of sleep or insufficient rest, improper food, and other con- 
ditions that lower the general vitality of the body. 

A special word concerning drafts is necessary. Drafts in them- 
selves cannot produce an infectious cold. The first s3'mptom of the 
disease is a chill, which is not the cause, but the effect, of the infec- 
tion. It is a common belief that the cold is caught when the chill 
occurs. The rigor frequently consists of only a transient chilliness, 
and it is during this time that the individual thinks he feels a draft 
which is producing his cold. 

Drafts have no appreciable injurious effect upon persons in good 
physical tone. They are, however, injurious to infants, the aged, and 
to susceptible individuals. Drafts are particularly apt to harm persons 
accustomed only to still, warm air. "It is not the engine drivers and 
firemen of trains that catch colds, but the passengers in the stuffy 
carriages." Coddling renders one susceptible to drafts, partty for the 
reason that the vasomotor impulses which contract the blood vessels of 
the skin are not sent out by the nervous mechanism, and consequently 


undue cooling of the part blown upon, and perhaps of the blood itself, 
takes place. Normally, when the wind blows upon the skin the vaso- 
motor contraction reduces the supply of blood and the tendency to 
cooling is further met by a stimulus which increases heat production. 
While it is true that a draft can no more cause an infectious cold than 
it can cause diphtheria, nevertheless, it is true that a draft may be the 
predisposing cause by which immunity is lowered. 

It is a mistake to think that the skin alone is involved in the ques- 
tion of drafts. The hardening of the skin as a prevention of colds is, 
therefore, a misnomer. The good effects of cold baths, exercise, fresh 
air, sunlight, and wholesome food do not consist in "hardening" the 
skin, but in improving the nutrition, stimulating the metabolism, help- 
ing the control of the nervous system, improving the tone of the vaso- 
motor system, strengthening the musculature, and enriching the blood. 

In preventing the ill effects of drafts, therefore, the entire organiza- 
tion of the body must be considered, and not the skin alone. 

Other important predisposing factors to colds are mechanical de- 
fects in breathing, or the filtering power of the upper respiratory pas- 
sages, also local pathological conditions, such as adenoids, polypus, 
deviation of the septum, chronic catarrhal conditions, all of which 
should receive appropriate treatment. 

One of the most important predisposing factors to colds is breathing 
vitiated and dusty air. Good ventilation, therefore, with air not too 
dry nor too warm, and the allaying of dust would prevent many a 
cold. The bacteria producing colds are frequently found in the mouth, 
nose, throat and teeth of persons in good health. Cleanliness and care of 
these parts is, therefore, an important consideration in the prevention 
of common colds. 


Cerebrospinal fever is an infection with the meningococcus (Dtplo- 
coccus intraceUitlaris meningitidis, "Weichselbaum). The essential le- 
sions of the disease are chiefly focused upon the meninges of the brain 
and cord. The disease occurs both in localized epidemics and sporadi- 

The meningococcus is a frail microorganism, closely resembling 
the gonococcus. Both are biscuit-shaped cocci; both grow feebly on 
artificial media. They are readily killed by drying, sunlight, heat, 
and other unfavorable conditions. They live a strict parasitic exis- 
tence and cause diseases peculiar to man, with lesions which resemble 
each other, both as far as the character of the inflammation and the 
distribution of the cocci within and without the cells are concerned. 
As a rule, these two microorganisms are usually distinguished by the 


source from "which they are obtained. Other^vise the differentiation is 
difficult and depends upon careful cultural and biological studies. 

All cases of meningitis are not caused by the meningococcus. Spo- 
radic cases may be due to the pneumococcus, streptococcus, bacillus of in- 
fluenza, the colon bacillus, the typhoid bacillus, the bacillus of bubonic 
plague, and of glanders. The gonococcus may also cause meningitis 
as a secondary complication. The epidemic form of cerebrospinal menin- 
gitis is always due to the meningococcus. Only one epidemic so far 
studied bacteriologically was certainly not due to the meningococcus; 
in this the microorganism responsible seems to have been the Strepto- 
coccus mucosus, or a close relative. 

The first epidemic outbreak of meningitis was reported by Yieus- 
seux in Geneva in 1805. The next year James Jackson, Thomas Welch, 
and J. C. Warren investigated an outbreak in Massachusetts. Since 
then numerous epidemics have occurred. In New York in 1904-05 
there were 6,755 cases and 3,455 deaths. 

The epidemiology of cerebrospinal fever differs from that of infantile 
paralysis in several respects. The seasonal prevalence of infantile paral- 
ysis follows the curve of the summer diarrheas (July to September), 
while cerebrospinal fever prevails especially in the fall and winter 
months. The seasonal prevalence of cerebrospinal fever is strikingly 
similar to that of pneumonia and influenza, and corresponds to a num- 
ber of diseases, such as scarlet fever, measles, diphtheria, and smallpox, 
in which the principal mode of infection is believed to be through the 
respiratory tract, and which are supposed to be spread mainly b}^ contact. 
The epidemics are usually localized. Country districts are more afflicted 
than cities. Children and young adults are most susceptible. Outbreaks 
sometimes occur in camp or on shipboard. The immunity produced by 
one attack is not lasting. Councilman reports five instances in which the 
same individual is reported to have had the disease twice. 

It is probable that the meningococcus enters the system through the 
mucous membrane of the nasopharynx. From this position it may reach 
the meninges directly through the lymph channels or indirectly through 
the circulation. The experiments of Flexner in the monkey indicate that 
when the meningococcus is introduced into the cerebral cavity it escapes 
by a reversed hinphatic current, so that under these circumstances it may 
be found in the mucous membrane of the nasophar}Tix. Fliigge, Weich- 
selbaum, Scheurer, and others have found the meningococcus present 
in great numbers in the nose and pharynx in most cases of the dis- 
ease during the first 12 days of illness. Park states that after the 1-ith 
day they cannot usually be found. The admirable monograph of Elser 
and Huntoon ^ includes a careful study of 210 cases of the disease. 
The most striking conclusion by these authors is 'the essential impor- 

"■ Journal of Medical Research, 1909, Vol. XX, pp. 377-536. 


tance of meningococcus carriers in the tranpmission of epidemic menin- 
gitis. Tiie number of persons who become such carriers during an 
epidemic of meningitis is far greater than the number of cases of ac- 
tual meningitis. Perhaps 70 per cent, of liealthy persons exposed may 
harbor meningococci in the respiratory passages. Apart from epidemics 
the meningococcus can be found but rarely in healthy individuals, but 
apparently there are persons who, once harboring this organism in the 
nasopharynx, carry it permanently and thus perpetuate the disease. 

Meyer, Voltmann, Furst, and Grieber ^ studied tlie question of car- 
riers in cerebrosj)inal meningitis. They found 1.73 per cent, of menin- 
gococcus carriers in over 9,111 healthy soldiers in the Munich garri- 
son at a time when no cerebrospinal fever was present. One exam- 
ination was made from each soldier. A special study was made of 
1,911 healthy persons wlio were examined many times, with the result 
that 2.-iG per cent, were found to be meningococcus carriers. Of the 
total of 11,U"32 healthy persons, about 2 per cent, examined contained 
the meningococcus in their throats. Isolation of the carriers had no 
influence on the incidence of the disease, and epidemiologically they 
found only exceptional relationship between the carriers and the sick. 
In one of the years during this study numerous clinical cases occurred; 
in another year none, although the number of carriers remained the same 
both years. The authors conclude that extreme painstaking cultural de- 
tection of meningococcus carriers is unnecessary in combating the spread 
of cerebrospinal meningitis; that the practical benefits do not justify 
the care and time necessary for such work. They believe that the chief 
foci, aside from factors not understood in the spread of this disease, 
seem to be the sick and especially the mild cases. Great care should, 
therefore, be taken to isolate the mild case so as to diminish the num- 
ber of carriers. On the other hand, in the epidemic of cerebrospinal 
meningitis in Texas in 1912, Thayer examined 421 persons; 59.6 per 
cent, were healthy carriers, as determined by the examination of stained 
smears. The results obtained from cultures showed 53.75 per cent, 
to be positive. 

It is now believed that cerebrospinal meningitis is transmitted prin- 
cipally through the medium of healthy carriers. Only a small percentage 
of the carriers develop the disease. The occurrence of more than one 
case in families is common. In the recent Texas epidemic there were 
many instances in which two members developed the disease, and in a 
smaller number three, four, and five members became infected. The 
disease is undoubtedly transmitted rather directly from person to 
person, for the meningococcus is of such low vitality that it suc- 
cumbs quickly to dr^'ing, sunlight, and other injurious influences. On 
account of its severity, persons suffering from the disease are decidedly 
^Miinchener Med. Wochenschr., 1910, No. 30, July 26. 


limited in their sphere of influence, and, as only a very small propor- 
tion of those who receive the microorganism are susceptible to it, the 
perpetuation and spread of meningitis must depend on the healthy car- 
riers who pass the meningococcus on from one to another until a sus- 
ceptible individual is infected and develops, meningitis. The virulence 
of the organism is also a determining factor. 

Prevention. — From our present knowledge preventive measures are 
clearly indicated, though very difficult to carry out. Epidemic cerebro- 
spinal meningitis is a good example of a group of diseases in which a 
more precise knowledge of the modes of transmission of the disease 
makes it obvious that prevention is a matter of extreme practical diffi- 
culty. Fliigge estimates that healthy carriers of this disease are ten 
times more numerous than recognized cases, and, therefore, are more 
than ten times as prolific a source of infection. "Wliile the isolation 
of the known cases will prevent a certain number of secondary cases, 
this measure alone cannot hope to control the disease. It is obviously 
impractical to undertake to make bacteriological examinations sufficient 
to discover all the carriers in a community of any considerable size; 
moreover, the control of so many carriers when discovered would re- 
quire military rule. We must frankly admit that when cerebrospinal 
meningitis has once become epidemic it cannot be stamped out by any 
known means of practical application. 

This does not mean that we should assume a supine attitude, for, 
even though the disease cannot be satisfactorily controlled, a certain 
number of secondary cases can be prevented. Every case and every sus- 
pected case should at once be reported to the health authorities and 
the patient isolated. The virus is contained especially in the discharges 
of the mouth and nose, and these secretions, should be disinfected. The 
house should be placarded, visiting prohibited, and isolation practiced. 
These measures will help diminish the number of carriers. 

Personal prophylaxis consists in avoiding the infection so far as 
possible, and in the use of antiseptic gargles and nasal douches. When 
the disease is epidemic people should keep away from large public gath- 
erings, crowded street cars, avoid the use of public drinking cups, and 
the like. They should be advised to exercise more than the usual care 
as to personal cleanliness. The closing of the schools may, under cer- 
tain circumstances, be justified. Urotropin in moderate doses has been 
suggested as a possible, though quite unproven, prophylactic. 

"While rigid quarantine is not, as a rule, effective in controlling this 
disease, localized outbreaks in institutions, military camps, or small 
towns may be kept from spreading by a strict system of isolation, even 
with a military cordon. 

Antimeningitis serum is useful in the treatment of the disease; it 
is not practical as a preventive. It must be introduced into the subdural 


space by lumbar puncture. The scrum should be provided free of cost 
or at a minimum price by health authorities. Further, boards of health 
should provide laboratory facilities for the bacteriological diagnosis of 
the disease, and the recognition of carriers. 

Sophian and Black ^ recommend an active immunization induced by 
inoculating killed cultures of the meningococcus. Tlie cultures are 
grown on 2 per cent, glucose agar, and after 18 hours' growth 
are washed off in distilled water, shaken for 20 minutes, heated at 50° C. 
for 1 hour, and tested for sterility. One million bacteria are injected 
at the first dose, 7 days later the same number, and 7 days later 2,000,- 
000. The injection of the dead meningococcus confers a considerable 
immunity, and may prove to be a valuable measure for personal prophy- 
laxis. Chronic carriers should be inoculated with the killed cultures, and 
their sphere of activity should be restricted. Furthermore, they should 
be impressed with the danger to tlieir fellowmen, and given careful in- 
structions concerning spitting, sneezing, coughing; the care of fomites, 
such as handkerchiefs, spoons, cups, etc. ; and the importance of cleanli- 
ness of the teeth, mouth, nose, and throat. 

> J. A. M. A., Aug. 17, 1912, LIX, 7, p. 527. 




The fact that disease may be transmitted through the bites of in- 
sects was suspected for years, but it was not until 1893 that it was 
demonstrated as a new principle by Theobald Smith in the case of 
Texas fever of cattle and the tick.^ Since then many diseases have 
been added to the list, which is constantly growing. We now know 
that some diseases are always transmitted through insects and others 
occasionally. A thorough comprehension of the subject is necessary for 
sanitarians and others in the fight against disease in all climates and 
in all places. 

It may be stated as a general law that, if a period of incubation 
in the insect is necessary, it indicates that the parasite probably be- 
longs to the animal kingdom and passes part of its life cycle within 
the insect. This constitutes the so-called extrinsic period of incubation. 
Malaria and yellow fever are examples of this class, which is spoken 
of as biological transmission. If, on the other hand, insects convey 
infection at once without a period of incubation in the insect, the trans- 
fer is a mechanical one; in this case the insect does not play the part 
of an intermediate host in the true biological sense, and there is no 
cycle of development of the parasite within the insect. These cases 
are almost all bacterial infections. 

It may be stated as a general rule that the insect hosts are not 
harmed by the parasites which they harbor and which are pathogenic 
for man. Thus, the malarial protozoon is pathogenic for man, but a 
saprophyte for the mosquito. The same is true of yellow fever and 
the Stegomyia, Texas fever and the tick, plague and the ilea, sleeping 
sickness and the tsetse fly, typhoid and the house fly, typhus fever and 
the louse, etc. 

The intermediate host in the zoological sense is that animal which 
harbors the asexual phase of the life cycle of the parasite; the definitive 

^ The other names associated with the early work upon insects and their re- 
lation to disease are: Manson, Finlay, Eoss, Grassi, and the U. S. Army Com- 
mission — ^Eeed, Carroll, Lazear, and Agramonte. 

14 181 


liost is the animal which haii)ors the poxual ])hasi\ Thus, in malaria 
man is the intermediate liost, the mosquito the definitive host. In 
jjopular ])arUince, the insects are spoken of as the intermediate liosts in 
all cases. 

Insects transfer infections mechanically in a variety of ways. The 
mouth parts, legs, or outer surfaces of the body may be smeared with 
tlie virus, which is thus simply carried to the lips, fingers or food, and 
thus enter the susceptible individual; or the virus may remain attached 
to the proboscis of a biting insect, thus transferring the infection very 
much as a hypodermic syringe would ; or the virus may be contained 
in the dejecta of the insect and be scratched or rubbed into the wound 
made by the bite; or the virus may be contained in the digestive tube 
or the body cavity and be released when the insect is crushed. 

Insect-borne infections are types of true endemic diseases, as they 
are necessarily limited in geographical distribution to the habitat of 
the insect host. 

As a rule, only one species, or at most a single genus, acts the part 
of a host for any particular infection, excepting in the mechanical 
transference of infection by insects. ]\Ialaria is confined to Anopheles, 
yellow fever to Stegomyia, Texas fever to the Margaropus annular- 
tiLS, sleeping sickness to the Glossina palpaUs, etc. This is a ques- 
tion of specificity. The specific nature of some of these diseases 
may be due to the fact that the parasite is not pathogenic for other 
hosts. Thus, yellow fever and malaria cannot be given to any other 
animal than man, even though large amounts of the infected blood be 
inoculated. The disease may be specific, in the sense that it is confined 
to one species, because the insect conveying the infection refuses to bite 
other than its own host. True specificity is found in all the cases of 
biological transference, whereas mechanical transference of infection 
may take place through widely separated genera. 

In some instances the virus is transmitted hereditarily through the 
insect from one molt to another, and even from one generation to the 
next. So far as known, however, hereditary transmission takes place only 
in those "insects" having an incomplete metamorphosis, such as the 
ticks. Brues suggests that the hereditary transmission of a virus is 
practically impossible in insects passing through complete metamorphosis, 
owing to the active phagocytosis during the pupal stage. 

Protozoa, bacteria, and even parasitic worms may be transferred 
by insects. The character of the disease cannot be predicated from 
the nature of the insect host. Thus, ticks convey Pirosoma and also 
spirochetes; flies convey trypanosomes, bacteria, the eggs of worms, and 
a variety of other infections; mosquitoes are concerned in the transmis- 
sion of the Plasmodium, a protozoon, filaria, a round worm, and a 
filterable virus (yellow fever). 



Insect-borne diseases may occur in great epidemics, as yellow fever, 
malaria, dengue, plague, relapsing fever, etc. When this occurs it 
means that the particular insect involved prevails in enormous num- 
bers in the epidemic area. 

Ticks and mites belong to the lower class of the Arachnida and 
are not, strictly speaking, insects (insecta), but are here considered 
in the same group for practical convenience. 

All the parasitic animals which live upon man and the higher ani- 
mals may act as go-betweens in the transportation of the microorgan- 
isms of disease. Parasites 

which live upon the skin 
are known as ectoparasites, 
in contradistinction to en- 
doparasites, which live 
within the body. The 
ectoparasites may be tem- 
porary parasites, as the 
mosquito ; or permanent, 
as the tick, which spends 
all but its earliest and last 
days attached to the skin 
of its host. Between these 
extremes there are para- 
sites spending more or less 
of their life attached to 
the host; thus, the bedbug 
and flea are temporary, whereas lice are permanent parasites. 

Many of the insect-borne diseases were formerly known as "place 
diseases.'' Thus, in yellow fever it was realized that the infection 
was not conveyed directly from man to man, but it was believed that 
the house or place became infected, and it was thought that the virus 
lived in the soil, upon the bedding, or on the clothing. This led to 
the notion that fomites or inanimate objects played an important role 
in the transference of disease. The early studies in bacteriology gave 
countenance to this view until our knowledge of the part played by in- 
sects and the importance of "contacts" has placed fomites in a subordi- 
nate and oftentimes negligible position. 

The prevention of the class of infections belonging to the insect- 
borne diseases depends upon a knowledge and thorough comprehension 
of three factors: (1) the disease, (2) the parasite, and (3) the insect. 
The suppression or control of the insect depends upon a thorough knowl- 
edge of its biology. Entomology, therefore, has become a vitally im- 
portant subject so far as preventive medicine is concerned. Without 
an acquaintance with the life history and habits of the insect host there 













■ '-vj 



Fig. 17. — A South African Blood-Sucking Fly 
(Pangonia), Illustrating Long Proboscis to 
Pierce Heavy Fur of Certain Animals. 


will be economic loss, wasted energy, and disappointing results. The 
malaria mosquito is active at night and breeds in tlie swamps; the 
yellow fever mosquito is active by day and breeds about houses. Other 
mosquitoes have their own particular breeding and hiding places. The 
su])pression of lice depends largely upon bodily cleanliness, the suppres- 
sion of the bedbug upon house cleanliness, the dangerous fleas come 
largely from association with other animals, the flies from manure and 
decomposing organic filth, the ticks from other animals and from the 
infested ground and woods. 

For the control of the insect-borne diseases it is not always neces- 
sary to exterminate the particular insect host. In fact, the extermina- 
tion of a particular species, much more a genus, is practically a biologic 
impossibility. A material reduction in the numbers of the insects in 
a particular area will often result in an elimination of the disease. 

The geographical distribution of the disease is always more lim- 
ited than the geographic distribution of the insect host. Anopheles 
exist in many places where there is little or no malaria. Stegomyia 
mosquitoes are numerous in the Philippines, but the infection has not 
yet been carried there. 

In the migration of insect-borne diseases it is usually the human 
host and not the insect that acts as the traveler. Insects, as a rule, 
do not go great distances of their own volition, and never over seas 
or from one country to another, unless taken in the conveyances of 
man or upon some higher animal. When yellow fever or malaria go 
from one country to another, the infection is translated in man. The 
infected mosquitoes are rarely transported, except occasionally upon 
wooden sailing vessels with water barrels that afford breeding places. 

An apparent exception to this statement is the case of plague. It 
is the rat rather than man that spreads plague from land to land. In 
this case, however, the disease is primarily an infection of the rat, which 
carries the flea along and man is secondarily attacked. Another excep- 
tion is the house and stable fly, which are known to travel a mile or 
more upon the wing. 

An effective campaign against mosquitoes, flies, or other in- 
sect pests requires the expenditure of time and money. Further, it 
requires the assistance of the entomologist, the engineer, and the prac- 
tical administrator. When the campaign involves extensive drainage 
or filling-in operations, this calls for the services of an engineer who 
has specialized along these lines. To attack the problem without a 
complete knowledge obtained from a careful study of the habits and 
breeding places of the particular species of insect will probably result 
in economic waste. Thus, in New Orleans, during the yellow fever 
campaign of 1905, much time and effort was saved by knowledge of 
the fact that the Stegomyia mosquitoes did not breed in the street gut^ 


ters of New Orleans. The habits and habitat of some species may vary 
in different localities, and a careful study of the local conditions is 
important to insure success. In the organization of a mosquito cam- 
paign the several branches of the work may be allotted to special divi- 
sions, each consisting of a foreman and crew. These men become 
skilled in their particular duties, and efficiency is thereby greatly pro- 
moted. One division should have charge of the oiling, another of the 
fumigation, another should seek to destroy the natural breeding places, 
another should attend to the screening, etc. In fly suppression one 
division should look after the storing and handling of horse manure, 
another to garbage and organic refuse, and so on. All the work must 
be centralized under the direction of one person with executive ability 
and a thorough understanding of the problem. 

The suppression of insects and household vermin is essentially a 
question of cleanliness. The most effective measures are those which 
strike at the breeding places, and these will be considered in detail un- 
der mosquitoes, flies, ticks, lice, fleas, and bedbugs. Next to the sup- 
pression of their breeding places, the most important measure in a 
household is to starve out these pests. Food must be so protected 
that insects, mice, and rats cannot gain access to it. Floors and other 
surfaces must be kept clean, so that they do not have the least film of 
organic dirt upon which insects feed. There should be no cracks or 
crevices to collect dust and dirt, which offer comfort for insect life. 
Cleanliness and incessant care must not only be exercised in the house- 
hold itself, particularly the kitchen, pantry, dining room, cellar, attic, 
and bathroom, but must also include the back yard and surroundings of 
the house. Old cans and broken bottles, rubbish, garbage, and general 
untidiness around the household afford breeding places, hiding places, or 
food for vermin. 

All the blood-sucking parasites must be regarded as dangerous. If 
they do not play the role of an intermediate host in the biological 
sense, they may occasionally transfer infections in a mechanical way, 
or the little wounds may allow the entrance of such infections as ery- 
sipelas, the pus cocci, anthrax, tetanus, and other microorganisms. Fur- 
ther, all blood-sucking parasites are potentially dangerous, in that 
new diseases may be established as the old ones must have been 
established at one time through the triple alliance of host, insect, and 

Science has demonstrated the danger from insects. Experience long 
ago decided that a healthy home must be free of insects and vermin of 
all kinds — it remains for the future to extend this kind of cleanliness 
to municipal housekeeping and rural sanitation. 

The principal insect-borne diseases, their causes, and the insect re- 
sponsible in each case are stated in the following table; 


Mau^uia (Lavoran, ISSO, the 
parasite) (Ronald Ross. 1895-8, 
relation to the mosquito) 

Plasmodium malaria: (Laveran) Anopheles 
Plasmodium vivax (Grassi & 

Feletti) | 

Plasmodium falciparum (Welch) 
Plasmodium immaculalum 


Yellow Fever (Reed, Carroll, A filterable virus 
Lazcar and Agramonte, 1900-2) i 

Stegomyia calopus 

FiL.\RL\sis (Dcniarquay, 1863)\ F ilaria bancrofti 
(Manson — also James) 

Culex fatigans. Anopheles niger- 
rimus and others 

Dengpe (Graham, 1903) (Ashburn A filterable virus 
and Craig, 1907) | 

[Culex fatigans 

DiSTOXiLVSi9-BiLH.\RZiosis (Bilharz, Schistosoma ■ha:matobium 
1851) (Katsurada, 1904) {Schistosoma japonicum 

Anopheles maculipennis (?) 


Nag.\na (Bruce, 1894) 

Trypanosoma brucei 

Tsetse fly (a biting fly) — (jto«s»no 

Sleeping Sickness (Button, 1901, 
and Todd) 

Trypanosoma gambiense 

Tsetse fly — Glossina palpalia 

Pappataci Feveb — 3-day feverj 
(Adriatic) (Doerr, 1909) 

Phlebotomus pappatasix — a dip- 
terous biting gnat 

'Pink Eye' 

A little fly or midge belonging to 
the genus Hippelales 

PmcLENT Ophth-^lmia of Egypt, 

Flies, el al. 

PouoMYELJTi8(Rosenau and Brues, 

A filterable virus coccal forms 
(Flexner and Noguchi, 1913) 

Stomoxys calcitrans — ^The stable fly 

Typhoid,'Cholera. Dysentery, etc. 
Contagious ophthalmia, ery- 
sipelas, anthrax, glanders and 
other skin infections, smallpox 
and other exanthems, etc. 

Mtisca domestica and other flies 
(Mechanical transmission) 


Texas FE^'ER (of cattle) (Th. Smith Pyrosoma bigeminum, now Ba- Margaropus annulatus 
& Kilborne, 1893) besia bigemina 

Rocky Mountain Spotted Fevtesi 
(Ricketts, 1906) 

<Dermacentor occidentalis (now 

I venustus) 

Atric.vnTickFea-er (Dutton, 1905) Spirochafa duttoni 

lOrnithodoros savignyi 

Relapsing FE\'ER(Obermcier, 1875) Spirochceta obermeieri 
(Ph. Ross and Milne, 1904) i 

\OrnithodoTos moubata or Argas 
I persicus 


Piroplasma canis 

L\ Spirillose des Poules (NLvr- 
CHOITC & Salembeni, 1903) 

(Ticks are not true Insecta.) 

SpirochcUa gallinarum 

Argas miniattis 


Relapsing FtvER (Obermeier, 1873) 

Spirochceta obermeieri 

Cimex lectularius, Ornilhodoros 
moubata, Argas persicus and 
perhaps other biting insects, as 
fleas and lice 


Trypanosoma leishmanii 

Cimex lectularius 

Cimex rotundatus 









Bacillus pestis 

LoemoTpsylla cheopis and other 


Ttphoid Fever (XicoUe, 1909) (?) 
(Ricketts & Wilder, 1910) 
(.■^derson & Goldberger, 1910) 

Pediculus vestimenti 
Also, Pediculus capilis 

A number of other diseases are suspected; thus, barbiero fever 
(Conorhinus megistu^) ; pellagra (Simulium) ; hookworm (Mu^ca 
domestica), etc. 


Practically all the germicidal agents are also insecticides. There 
are some exceptions to this statement, notably formaldehyde, which is 
one of our most potent germicides, but has little or no effect upon in- 
sect life in its gaseous state. 

The action of insecticides may be considered under three classes: 
(1) those that act as general protoplasmic poisons, such as strong acids 
or alkalies, hydrocyanic acid, sulphur dioxid, etc.; (2) those that suf- 
focate the insects, such as oily substances, and (3) those that act upon 
the nervous structures, such as chloroform, ether, and other general 

Another classification considers insecticides under four groups: (1) 
those used by contact in liquid form or in solution; (2) those used 
by contact in dry or powdered form; (3) those used by contact in 
vapor form; (-i) those used by mixing with food and which are 
poisonous when ingested. Insects differ markedly in their power of 
resisting insecticides. Those with well-developed chitinous protection, 
such as bedbugs and roaches, are more difficult to kill than flies, fleas, 
and mosquitoes. 

The most practical of the insecticides for the destruction of the 
winged insects in an enclosed space are those that may be used in the 
gaseous state. Of these, sulphur dioxid, hydrocyanic acid gas, carbon 
bisulphid, or carbon tetrachlorid are most commonly employed and are 
most reliable. The uses and limitations of these and other insecticidal 
agents will now be considered in detail. 

Preparation of the Room for Fumigation. — It is more important to 
tightly seal a room in which insects are to be destroyed than where 
only a germicidal action of the gas is looked for. Insects may escape 
through minute openings, and they may hide in nooks and corners 



where the gas permeates slowly and feebly, or may take cover under 
the folds of crumpled paper or folded fabrics, and thus escape the in- 
secticidal action of the gas. Self-preservation tempts mosquitoes and 
other insects as well as rats and mice to seek the light when in the 
presence of an irritating gas. It is, therefore, convenient to darken 
the place to bq treated, leaving one source of light. The dead vermin 
may then be readily collected about this place. 

Strips of paper should be pasted over doors and windows. Cracks 

and crevices may be 
caulked with tow- 
els, waste, or other 
suitable substance. 
Ventilators, f i r e- 
places, hot-air reg- 
isters, and all open- 
ings into the room 
must be covered, 
otherwise both the 
gas and the insects 
will escape. Closets 
and small doors 
should be opened 
and all the drawers, 
lockers, and similar 
places exposed in 
such a way that the 
gas may have free 
access to remote 
corners. Furniture 
should be moved 
away from the 
walls. Fabrics, 
paintings, instru- 
ments, bright metal 
work, or other ob- 
jects liable to injury may be removed or covered, especially when sulphur 
is used. 

The Relative Efficiency of Insecticides. — McClintock, Hamilton, and 
Lowe ^ have tested a number of insecticidal substances, the values of 
which are shown in Table 4, which gives a list of the substances 
tested and the species of insects used in the experiments, together with 
the quantity of each substance which, when properly transformed into 
vapors, was sufficient to kill the species indicated. The coefficient eol- 
Wour. Am. Pub. Health Assn., Vol. II, No. 4, Apr., 1911, p. 227. 

FiQ. 18. — Example of Sealing DooBa for Purpose of 



umn Bhows the inverse ratio between this quantity and 8 grams, the 
weight of sulphur which, when burned, kills the bedbug in the 800,000 
c. c. of inclosed space. 

The efficient dilution of the vapors of any substance may be ob- 
tained from this coefficient by multiplying by 100,000. 

For example, if one wishes to use carbon disulphid, by consulting 
No. 28 in the table it is shown that 24 grams were required to kill 
bedbugs, while only 8 grams were required of sulphur. It is therefore 
only one-third as strong and its coefficient is 0.3-[-. Its efficient dilu- 
tion is 33,000. 



Time of exposure — Varied as conditions required. 

Column 1 — Quantity used to kill the specified insect. 

Column 2 — Coefficient of efficiency compared with the efficiency of sulphur dioxid on bedbugs 







1 Sulphur Dioxid as Sulphur. . . 

2 P j-ridin 

3 Pyridin Bases (Merck) 

4 QuinoLLn 

5 Creosote Oil 

6 Carbolic Acid 

7 Naphthalene 

8 Kerosene 

9 Anilin Oil 

10 Cedar Oil 

11 Citronella OU 

12 Cloves Oil 

13 Peppermint Oil 

14 Pennyroyal Oil 

15 Australene 

16 Turpentine (Oregon Fir) 

17 Oil Pinus Palustris 

18 Oil Turpentine 

19 Turpentine (Mich. Wood).. . . 

20 Benzaldehyde 

21 Nitrobenzol 

22 Ammonia 28% 

23 Alcohol, Ethyl 

24 Alcohol, Methyl 

25 Acetone 

26 Chloroform .' 

27 Ether (Ethyl Oxide) 

28 Carbon Disulphid 

29 Carbon Tetrachlorid 

30 Chloretone 

31 Camphor 

32*Nicotin, 80% Sol 

33 Hydrocyanic Acid, as Potas- 

sium Cyanid 

34 Paraform 

SSJFormaldehyde 40% Sol 

36 Stramonium Leaves 

37 Sabadilla Seeds 

38 Chrysanthemum Flowers . . . . 

4 + 


8 + 
16 + 

6.3 + 
11.5 + 

4 + 

4 + 

4 + 

8 + 

8 + 
36 + 
16 + 
20 + 
16 + 

4 + 

8 + 
36 + 
80 + 
80 + 
40 + 
40 + 



























4 + 

16 + 

6.3 + 

4 + 

4 + 

4 + 

8 + 

8 + 
36 + 
16 + 
20 + 
24 + 

4 + 

36 + 
80 + 
80 + 
40 + 
40 + 


4 + 
8 + 


8 + 
54 + 

8 + 
80 + 






40 + 

4 + 


8 + 
54 + 

8 + 
80 + 






































4 + 







36 + 



20 + 
80 + 
80 + 
40 + 
16 + 

15 + 

40 + 



16 + 
10 + 




























4 + 


16 + 



36 + 
80 + 
80 + 
40 + 
16 + 

40 + 



16 + 

10 + 

16 + 






























4 + 



80 + 
14 + 
16 + 















The + sign after a number indicates that this quantity was the largest used and that it was 

* Coefficient of nicotin based on 100% alkaloid. 
% Quantity of formaldehyde to be an efficient germicide is 13J^ c. c. or a coefficient of 0.625. 


The best methods of generating gases for fumigating purposes are 
considered below. For further information concerning these substances, 
with special reference to tlieir germicidal action, see Section XII. 

To insure success the gas used to fumigate a room should be liber- 
ated in a large volume in a short time. If the gas is evolved slowly 
much of it will be lost before the room can become charged with a 
sufficient amount to kill the insects. 

The amount of gas and the time of exposure stated in each case 
are the minimum. When large, leaky, or irregularly shaped spaces are 
to be fumigated, the amount of gas should be increased and the time 
of exposure prolonged. It is also advisable to generate the fumes 
in as many different places as practicable, as this favors rapid diffu- 

Sulphur. — Sulphur is one of the most valuable insecticides we pos- 
sess. It may be used either as a gas — SOo — or in its powdered form 
— flowers of sulphur. 

Sulphur dioxid is destructive to all forms of life. It will kill 
mosquitoes, flies, fleas, roaches, bedbugs, and all kinds of vermin, in- 
cluding rats and mice. While sulphur dioxid is one of the most de- 
pendable insecticides it is a rather feeble germicide. It is limited 
in practice on account of its destructive and corrosive action. This 
destructive action results from the sulphurous acid and sulphuric 
acid produce'd in the presence of moisture. Fortunately the dry gas 
is quite as poisonous to mosquitoes, flies, rats, mice, etc., as the moist 
gas. Dry sulphur dioxid, however, has absolutely no germicidal value. 
Dry sulphur dioxid does not tarnish metals, does not rot fabrics, and 
does not bleach pigments. Fumigation with SO, may, therefore, be done 
with little damage to property on dry days. Metal work, fabrics, and 
pigments that cannot be removed from the room may be protected from 
the sulphur fumes by simple mechanical devices. 

Sulphur dioxid may be produced either by burning sulphur or by 
liberating liquefied sulphur dioxid. The methods of generating the 
gas will be found on page 997. One pound of sulphur burned for 
each thousand cubic feet of air space or two pounds of liquefied sul- 
phur dioxid and an exposure of two hours is sufficient to kill mos- 
quitoes, flies, and other insects in a small tight space. Three to four 
hours are ample for rats and mice. If the space is large or leaky the 
amount of gas should be increased and the time of exposure prolonged. 
Sulphur dioxid has surprising power of penetration through clothing 
and fabrics. In very dilute proportions it will in one hour's time kill 
mosquitoes even when hidden in eight layers of toweling. It has ab- 
solutely no power of penetration when used as a germicide. This sub- 
stance, which has so long been disparaged as a disinfectant because it 
fails to kill spores and many spore-free bacteria under certain condi- 


tions, must now be considered as holding first rank as an insecticide. 
For consideration of sulphur dioxid as a germicide see page 997. 

Flowers of Sulphur. — Sulphur in its dry, powdered state is use- 
ful against a number of parasites. In this form, however, it has little 
use as an insecticide in preventive medicine, not being efficacious against 
bedbugs, ants, roaches, or fleas. 

It may be applied in several ways, the simplest of which is to 
sprinkle the dry sulphur about the places where insects are found. 
Flowers of sulphur may also be combined advantageously with other 
insecticides, such as kerosene emulsion, resin wash, or soap Avash. It 
should first be mixed into a paste and then added to the spray tank 
in the proportion of about 1 or 2 pounds to 50 gallons. It is particu- 
larly efficacious for the destruction of the mites and rust of plants 
and fruits. 

Sulphur in the form of an ointment is particularly obnoxious to 
ticks and other ectoparasites. The itch-mite (Sarcojites scahiei) is 
very susceptible to the flowers of sulphur, which is, therefore, one of 
the ingredients of almost all ointments used in this skin affection. 

Sulphur dips are used to destroy the mites on domestic animals. 
These dips ordinarily contain 1 part of lime to 3 parts of sulphur or 
tobacco. It is common experience that, while these sulphur dips may 
be depended upon to destroy the mites, they do not destroy the eggs, 
hence the treatment should be repeated in about 10 days, which per- 
mits time for the eggs to hatch and develop into adults. 

Formaldehyde. — Formaldehyde, while holding the front rank as a 
germicide, is a feeble insecticide. The gas seems to have no effect 
whatever upon roaches, bedbugs, and insects of this class even after 
prolonged exposure to very high percentages. As a differential poison 
formaldehyde gas is a very remarkable substance. It destroys bacteria 
almost instantly, but, while it is irritating to the higher forms of ani- 
mal life, it is not very toxic. I have repeatedly found that roaches and 
other insects with strong chitinous protection seem unharmed after 
12 hours' exposure to formaldehyde gas in very strong atmospheres 
of the gas, in air-tight disinfecting chambers. Mosquitoes may live in 
a weak atmosphere of the gas over night. It will kill them, however, if 
the gas is brought in direct contact with them in the strength and time 
prescribed for bacterial disinfection. 

When a weak insecticidal gas is used it is much more difficult to 
obtain direct contact between the gas and the insects than between 
the gas and germs, because the sense of self-preservation aids the for- 
mer in escaping from the effects of the irritating substance. Mos- 
quitoes and other insects hide in the folds of towels, bed clothing, 
hangings, fabrics, and out-of-the-way places where the formaldehyde 
gas does not permeate in sufficient strength to kill them. The gas is 


polymerized and deposited as paraforni on the surface of fabrics which 
prevent its penetration, and hirge quantities arc lost by being absorbed 
by the organic matter of woolen fabrics. Mosquitoes have a lively in- 
stinct in finding cracks or chinks where fresh air may enter a room 
or other places where the gas is so diluted that tliey escape destruc- 
tion. Therefore, formaldeliyde gas, as well as other culicidcs, cannot 
be trusted to kill all the mosquitoes in a room which cannot be tightly 
sealed. On account of its feeble action, formaldehyde is not recom- 
mended as reliable. 

For the l)est methods of evolving formaldehyde gas, the quantities 
to be used, and other details of the process, see page 993. 

Formaldehyde gas in watery solution, known as formalin, is use- 
ful for the destruction of flies. Small quantities of dilute formalin 
(4 per cent.) placed in saucers about the room attract flies. They 
drink the fluid, wliich soon kills them. 

Pyrethrum. — Pyrethrum is a popular and much used insecticide be- 
cause it is comparatively cheap and non-poisonous to man and the 
higher animals. It is also non-corrosive, but unfortunately it is not 
very powerful for the destruction of roaches, ants, bedbugs, flies, fleas, 
mosquitoes, etc. It has no germicidal action. 

Pyrethrum, also sold under the names of Buhach or Persian insect 
powder, or simply "insect powder," is the flowers of the Chrysanthemum 
roseum and the Chrysanthemum carneum, both hardy perennials and 
resembling camomile in appearance. According to Kalbrunner, 4 grains 
of the pure powder sprinkled on a fly in a vial should stupefy it in 
one minute, and kill it in 2 or 3 minutes. . It acts on insects exter- 
nally through their breathing pores. When brought in direct con- 
tact with them it is fatal to many forms of biting and sucking in- 
sects, such as roaches, flies, and ants. It may be used either as a dry 
powder or by its l)urning fumes. As a dry powder it may be used 
pure or mixed with flour, in which form it should be puffed about the 
room, especially into cracks. 

When pyrethrum powder is ignited it smolders, giving off fumes 
which stun, but do not always kill, mosquitoes.^ It is not, therefore, 
a dependable insecticide. This uncertainty and the price of pyrethrum 
restrict its field of usefulness. 

Pyrethrum fumes do not corrode metals or act injuriously upon 
fabrics and pigments. However, a slight brown deposit is occasionally 
left on exposed surfaces which may stain linen a yellowish color. This 
deposit or stain is readily washed out, or soon fades. 

Pyrethrum powder has been used very much in those cases where 
sulphur is prohibited on account of the danger of damage to paintings, 

* Tobacco smoke and other substances which produce dense fumes, particu- 
larly those containing pyroligneous products, will kill mosquitoes. 


fabrics, tapestries, metal work, musical instruments, upholstered furni- 
ture^ and the like. It is used in the proportion of 2 pounds per 1,000 
cubic feet of air space, the exposure being for not less than 4 hours. 
As its insecticidal effect is uncertain, it is necessary carefully to sweep 
up and burn all the mosquitoes that have been stunned and are ap- 
parently dead after the fumigation. Most of these mosquitoes will be 
found on the window sill or on the floor close to the window, where 
they are attracted by the light in their efforts to find an exit to es- 
cape the fumes. Advantage should be taken of this tendency of the 
mosquito to seek the light by darkening all but one window. 

Sheets of paper containing some sticky preparation may be placed 
upon the floor and upon the window sill in order to catch the mos- 
quitoes. A satisfactory adhesive preparation may be made by dissolv- 
ing, by the aid of heat, 65 parts of colophony resin in 35 parts of 
castor oil. This simplifies the collection and disposal of the insects. 

Pyrethrum powder should be distributed in pots or pans and set on 
fire with a little alcohol, which should first be sprinkled over it. The 
quantity apportioned to any one pot or pan should not exceed 1% 
inches in depth, if the exposure is to be for 4 hours. The pots and 
pans should be set on bricks to prevent scorching the floor. 

Much of the pyrethrum upon the market is impure, which further 
weakens what is a feeble insecticide at best. 

Phenol-camphor (Mini's CuUcide). — Camphophenique or phenol- 
camphor is prepared by rubbing up equal weights of phenol crystals and 
camphor. It may be more conveniently prepared by first liquefying the 
phenol by gentle heat and then pouring it over the camphor. The cam- 
phor and phenol combine to form a new chemical compound, which re- 
mains fluid at ordinary temperatures. This preparation was first used 
on a considerable scale during the yellow fever epidemic in New Or- 
leans toward the close of 1905 at the suggestion of Mr. Mim, the city 
chemist. At this time I took the opportunity of making a number of 
tests with Dr. Metz concerning the culicidal value of this substance. 
The effect of the fumes on mosquitoes was later studied by Berry and 
Francis. When phenol-camphor is moderately heated it gives off dense 
fumes, which rise rapidly and diffuse slowly, and after 30 to 60 min- 
utes, depending upon the amount employed and the temperature of the 
air, the fumes condense and are deposited as a slight moisture on all 
exposed surfaces. As a culicide phenol-camphor may be compared to 
pyrethrum; the fumes stun the mosquitoes, but do not invariably kill 
them. The fumes are somewhat irritating to the mucous membranes, 
especially the eyes; they may cause dizziness, headache, cloudy urine, 
and other mild symptoms of phenol poisoning in susceptible individuals 
much exposed to their inhalation. The fumes of phenol-camphor do 
not tarnish metals, rot fabrics, or bleach pigments. They, however. 


have the disagreeable property of softening the varnish of surfaces on 
which tliey condense. On account of its slight power of diffusion, rela- 
tively high cost, and uncertainty of action, it cannot take the place of 
sulphur except in the parlor, pilot house, and other compartments where 
sulphur is prohibited on account of the damage it produces. Compared 
with pyrcthrum, phenol-camphor is less expensive, more certain, and 
not so objectionable to the housekeeper. Its use involves a little more 
care and intelligence than that required for the simple burning of py- 
rethrum. If it is overheated it will take fire, and no culicidal action 
is produced. Goldberger concludes that, for use on a large scale, as 
in times of epidemics, in the hands of trained fumigators, phenol-cam- 
phor is, on the whole, to be preferred to pyrethrum, being more easily 
transportable on account of the small bulk required, and because the 
fumes condense quickly and the room may, if desired, be entered in an 
hour and the apparatus removed, thus making it possible to fumigate 
a larger number of rooms in a given time with less labor than in the 
case of either sulphur or pyrethrum. 

Phenol-camphor is used in the proportion of 4 ounces to every thou- 
sand cubic feet of air space, and with an exposure of 2 hours. In this 
proportion and time the film of condensation is slight and is rapidly dis- 
sipated after the doors and windows are opened. The preparation of 
the room is the same as that described above. The phenol-camphor ap- 
portioned to the room to be fumigated should be distributed in agate- 
ware basins, not more than 8 to 10 ounces to any one basin. Each 
basin is set over an alcohol lamp at such an elevation and in such a 
manner as will permit a rapid evolution of the fumes. Care must be 
taken not to heat the basin so quickly as to cause the liquid to become 
overheated and take fire. This point must first be determined experi- 
mentally for each type of lamp used. One of the small brass alcohol 
vapor lamps to be found on the market serves excellently. As a safe- 
guard against accidents the lamp should stand in a pan containing about 
one-half inch of water. The basin containing the phenol-camphor may 
be set upon a section of galvanized iron stove-pipe, at one end of which 
sectors are cut out so as to form legs of a length equal to the height 
of the lamp; just below the upper margin of the pipe a series of holes 
are punched so as to provide for draft. The stove-pipe should be of 
such a length as to support the basin containing the phenol-camphor 
about 10 inches above the flame. This ingenious and simple device, 
suggested by Berry and Francis, acts as a chimney, protects the flame, 
is relatively cheap, and has proven satisfactory. 

Hydrocyanic Acid Gas. — Hydroc^^anic acid gas is extremely poison- 
ous to all forms of life. It kills roaches, bedbugs, mosquitoes, fleas, 
flies, rats, mice, and other vermin with great certainty and very quickly. 
It is much less poisonous to the higher forms of vegetable life, al- 


though it has a certain amount of germicidal power. Hj'drocyanic acid 
gas is much used in greenhouses for the destruction of insect pests and 
for scale and other parasites of fruit trees. The gas has a distinct 
place in the disinfection of granaries, stahles, ships, barns, outhouses, 
railroad cars, and other uninhabited structures infested with "vermin. 
It is also extensively used in flouring mills against weevils, in rail- 
road cars against bedbugs, and in tobacco warehouses against insects in 
general. It should be used in the household onlv with the greatest 
precaution, as the least carelessness with it would jDrobably mean the 
loss of human life. It has the marked advantage that it does not harm 
metals, fabrics, or j)igments, and may be used in the most expensive 
drawing rooms. 

Hydrocyanic acid gas is lighter than air and has an agreeable 
aromatic odor quite familiar in the flavoring essence of bitter almonds. 
The best method of generating it for the purj^ose of fumigation is by 
the action of dilute sulphuric acid upon potassium cyanid, in the fol- 
lowing proportions : 

Potassium cyanid 1.0 part 

Sulphuric acid 1.5 parts 

Water 2.25 parts 

The first step is to dilute the acid, which is done by adding the 
acid to water in a vitrified clay jar or receptacle capable of withstand- 
ing the heat. The whole amount of cyanid must be put into the acid at 
once. As the evolution of the gas is very rapid, the operator should 
be ready to leave the spot immediately. As pointed out by Fulton, it 
is convenient to tie the cyanid up in a bag made of cheese cloth or tissue 
paper, which is lowered into the acid by a cord passing outside of the 
room. The amount of gas used for plant fumigation, expressed in terms 
of cyanid, is about 1 ounce per 100 cubic feet; about the same quantity 
is effective as an insecticide in rooms and confined spaces. Hydrocyanic 
acid gas is quite as effective as sulphur dioxid, is not destructive, is 
reasonably cheap, and is certain in its action, but its poisonous nature 
is such a serious drawback that it has a limited place as an insecticide 
in the disinfection of houses. 

BisulpMd of Carbon. — Bisulphid of carbon (CSo) is a very efficient 
insecticide, but a dangerous one, on account of its inflammable and ex- 
plosive nature. It quickly kills mosquitoes, roaches, flies, ants, and 
insects of all kinds, as well as rats, mice, and squirrels. Wlien pure it 
is a mobile, colorless liquid with an agreeable ethereal odor, but often 
it has a more or less fetid odor from the presence of other volatile 
compounds. The liquid must be kept in well-stoppered bottles in a cool 
place, and away from the light and fire. It evaporates rapidly at ordi- 


nary temperatures, so that in using this substance in a confined space it 
is sufficient to pour it into open pans. Carbon bisulphid is very in- 
flammable — more so tlian ether — and burns witli a pale blue flame 
yielding sulphur dioxid and carbon dioxid or monoxid. In its use 
every precaution must be taken to see that there is no fire, lighted 
cigar, etc., in or about the field of operation. On account of its poison- 
ous nature, if used in a house or other inhabited structure, the rooms 
must be thoroughly aired after its use. 

According to Hinds, shallow tin pans or plates make good evaporat- 
ing dishes for carbon bisulphid. The larger the evaporating area the 
better. About one square foot of evaporating surface is used to every 
25 square feet of floor area, and one-half to one pound of the liquid 
carbon bisulphid is used for each square foot of evaporating surface. 
These figures, of course, are only suggestive and approximate. The 
pans should be placed as high in the room as possible, since the vapor 
is so heavy that it settles rapidly. Care should be taken when placing 
the pans to see that they are nearly level so as to hold the liquid, though 
ordinarily no particular harm will be done if some of it is spilled. It 
should not be found necessary to lose time in adjusting such things after 
the operation has begun. 

Carbon bisulphid is being extensively used in California in the 
plague campaign. A piece of waste the size of an orange is saturated 
with the liquid and the wet ball placed in the mouth of the squirrel 
hole. Wet clay is then stamped into the warren so that the gas which 
is generating may have no opportunity to escape. All of the holes of 
the burrows are treated in this way. In some instances the ball is 
placed deeply in the hole and then ignited. This is more or less dan- 
gerous, as an explosion occurs, and, while the gas is thus disseminated 
to all parts of the warren, its action only covers a limited period of 
time, and is, therefore, not as certain as simply allowing the carbon 
bisulphid to evaporate. It not only kills the squirrels, but also the 
fleas on them. Carbon tetrachlorid may be used in place of carbon 
bisulphid. It is just as poisonous but neither inflammable nor explosive. 

Petroleum. — Petroleum, kerosene, or coal oil is a very valuable in- 
secticide, but of limited application, as it must be used in liquid form. 
As a remedy for mosquitoes it is applied in the proportion of al)0ut 1 
ounce to 15 square feet of water surface. It should form a uniform 
film over the surface, and will then destroy the larva3 and pupae of 
the mosquito and the adult females coming to the water to lay their 
eggs. The oil must be renewed every week or two, depending upon 
the temperature and other conditions. A light grade of fuel oil is 
best for this purpose (see page 203). 

Petroleum is also useful against roaches, bedbugs, fleas, lice, and 
other insect vermin when used by direct application or by spraying. 


either in the form of the pure oil or as an emulsion. Petroleum is 
very efficient against fleas. Frequent application to the floor or other 
places will keep away ants^ and by direct application to the breeding, 
feeding, and traveling places it is a useful remedy against household 
vermin in general. By direct application to the head or other parts 
affected, coal oil is the cheapest and most effective remedy for lice. 

Emulsion of crude petroleum for. application to the skin of animals 
or to trees, or other plants, or for general insecticidal purposes is made 
from the formula of T. M. Price: 

Crude petroleum 2 gallons 

Water % gallon 

Hard soap % pound 

Dissolve the soap in the water with the aid of heat. To this add 
the crude petroleum; mix with a spray pump or shake vigorously and 
dilute with the desired amount of water. The emulsion of crude petro- 
leum made according to this modified formula remains fluid, and can 
be easily poured. It will stand indefinitely without any tendency 
toward separation of the oil and water, and can be diluted in any pro- 
portion with cold soft water. 

Arsenic. — The arsenical compounds, according to Marlatt,^ have sup- 
planted practically all other substances as a food poison for biting in- 
sects. The two arsenicals in most common use obtainable everywhere 
are arsenate of lead and Paris green. Scheele's green and arsenite of 
copper are less known and less easily obtainable, but in some respects 
are better than Paris green. The use of powdered white arsenic is not 
recommended on account of its corrosive action, as well as the fact that 
it is ai)t to be mistaken for harmless substances. 

The arsenical poisons may be applied in one of three ways: (1) in 
suspension, as poisoned waters, mainly in the form of sprays; (2) as a 
dry powder blown or dusted about the infested areas; or (3) as 
poisoned bait. 

It must be remembered that the arsenicals are very jDoisonous, and 
should be so labeled, and care taken to prevent accidents. 

Paris geeen is a definite chemical compound of arsenic, copper, 
and acetic acid (acetoarsenite of copper), and should have a nearly 
uniform composition. It is rather a coarse powder, or, more properly 
speaking, crystal, and settles rapidly in water, which is its greatest fault 
so far as the making of suspensions of this substance is concerned. The 
cost of Paris green is about 20 cents per pound. 

ScHEELE^s GREEN is similar to Paris green in color and differs from 
it only in lacking acetic acid; in other words, it is simply arsenite of 

^Farmers' Bulletin No. 19, U. S. Dept. of Agriculture. 


copper. It is a finer powder than Paris green, and, tlierefore, is more 
easily kept in suspension, and has the additional advantage of costing 
only half as much per pound. 

Arsexite of lead is prepared by combining, approxiinately, 3 parts 
of the arsenite of soda with 7 parts of the acetate of lead (white sugar 
of lead) in water. These substances, when pulverized, unite readily 
and form a white precipitate, which is more easily kept suspended in 
water than any of the other arsenical poisons. Bought at wholesale, the 
acetate of lead costs about 7I/2 cents a pound, and the arsenite of soda 
costs about 7 cents a pound. Its use is advised where excessive strengths 
are not desirable, and upon delicate plants, wliere otherwise scalding is 
likely to result. 

An average of one pound of either Paris green or Scheele's green, or 
London purple to 150 gallons of water is a good strength for general 
purposes in using the wet method. The powder should first be made 
up into a thin paste in a small quantity of water, and, if the suspen- 
sion is to be used upon plants, vegetables, or about foliage, an equal 
amount of quicklime should be added to take up the free arsenic and 
remove or lessen the danger of scalding. 

For the distribution of dry poison the arsenicals are diluted with 
10 parts of flour, lime, or dry gypsum. 

The following mixtures are used in the form of sprays, to destroy 
insects and fungi upon plants.^ The arsenate of lead mixture has been 
much used in Massachusetts with success against the gipsy moth and 
other destructive insects upon trees and plants. These mixtures are 
equally useful as insecticides wherever sprays or local applications are 


Arsenate of soda (5 per cent, strength), 4 ounces. 
Acetate of lead, 11 ounces. 
Water, 100 gallons. 

Put the arsenate of soda in 2 quarts of water in a wooden pail, and 
the acetate of lead in four quarts of w^ater in another wooden pail. 
When both are dissolved, mix with the rest of the water. Warm water 
in the pails will hasten the process. For the elm-leaf beetle use 10 
instead of 100 gallons of water. 

A number of ready-made arsenates of lead are now on the market, 
and, except when very large amounts are needed, it will prol)ably prove 
cheaper to buy the prepared material than to make it. With this 
ready-made material take 3 pounds to 50 gallons of water for codling 
moth, and 5 pounds to 50 gallons to the elm-leaf beetle and on potatoes. 

'From BuUetin No. 123, April, 1908, of the Massachusetts Agricultural 
Experiment Station by Stone and Ferald. 


White arsenic, 2 pounds. 
Sal-soda, 8 pounds. 
Water, 2 gallons. 

Boil till the arsenic all dissolves — about 45 minutes. Make up the 
water lost by boiling and place in an earthen dish. For use take one 
pint of this stock, 2 pounds freshly slaked lime, and 45 gallons water, 
and spray. 


Hard soap, shaved fine, % pound. 
Water, 1 gallon. 
Kerosene, 2 gallons. 

Dissolve the soap in the water, which should be boiling; remove 
from the fire and pour it into the kerosene while hot. Churn this with 
a spray pumj^ till it changes to a creamy, then to a soft, butter-like, 
mass. Keep this as a stock, using one part in nine of water for soft- 
bodied insects, such as plant lice, or stronger in certain cases. 

Pulverized resin, 5 pounds. 
Concentrated lye, 1 pound. 
Fish or other animal oil, 1 j)int. 
Water, 5 gallons. 

Place the oil, resin and one gallon of hot water in an iron kettle 
and heat till the resin softens; then add the lye and stir thoroughly; 
now add 4 gallons of hot water and boil till a little will mix with cold 
water and give a clear, amber-colored liquid; add water to make up 5 
gallons. Keep this as a stock solution. For use take: 

Stock solution, 1 gallon. 
Water, 16 gallons. 
Milk of lime, 3 gallons. 
Paris green, ^ pound. 

Copper sulphate (blue vitriol), 4 pounds. 
Lime (unslaked), 4 pounds. 
Water, 25 to 50 gallons. 

Dissolve the copper in hot or cold water, using a wood or earthen 
vessel. Slake the lime in a tub, adding the water cautiously and only 


in sufficient amount to insure tliorougli slaking. After thoroughly 
slaking, more water can be added and stirred in until it has the con- 
sistency of thick cream. When l)(ith are cold, dilute each to the re- 
quired strength and pour both together in a separate receptacle and 
thoroughly mix. Before using, strain through a fine mesh sieve or a 
gunny cloth; the mixture is then ready for use. 

If the amount of lime in the Bordeaux mixture is insufficient there 
is danger of Imrning tender foliage. In order to obviate this, the mix- 
ture can be tested witli a knife blade or with ferrocyanid of potassium 
(1 oz. to 5 or G oz. of water). If the amount of the lime is insufficient, 
copper will be deposited on the knife blade, while a deep brownish-red 
color will be imparted to the mixture when ferrocyanid of potassium 
is added. Lime should be added until neither reaction occurs. A slight 
excess of lime, however, is desirable, and it is seldom one has to apply 
these tests. 

The Bordeaux mixture is a good fungicide, but is less useful as an 


Mosquitoes differ markedly in their habits. Some species may be 
classed as domestic aninuils l)ecause they are commonly or almost ex- 
clusively found in or close to human hal)itations. This is notably the 
case with Stegomyia calopiis, the yellow fever moscpiito; Culcx pungens, 
the intermediary for Filarta hancroftli (filariasis) ; and Culex faligans, 
the carrier of dengue fever. The sylvan -or wild mosquitoes, of which 
the Culex sollicitans, the common salt marsh mosquito of our Atlantic 
coast, is a well-known example, are seldom met with in human habita- 
tions. A third or semi-domestic class may be encountered either in 
or near houses, or in fields or swamps. This class includes the malarial 
mosquitoes belonging to the genus Anopheles. 

The adult mosquito may be carried to considerable distances by 
winds; but of its OM-n volition it does not ordinarily travel outside of 
a radius of half a mile from its Ijreeding phice. Most species do not 
fly nearly so far. This moans that the destruction of all lireeding places 
within a comi)aratively small radius of a habitation will rid it of all 
but those mosquitoes which are blown in by the winds from more or 
less distant marshes, or which are brought in the vessels and vehicles 
of trade and travel. 

life History and Habits. — Mosquitoes pass through four stages: 
(1) the egg or eml)ryo, (■.^) the larva, (3) the pupa, and (4) the imago 
or adult winged insect. The Qg^, larval, and ])upal stages are aquatic. 
Mosquitoes never breed in damp grass, weeds, or bushes, as is popularly 
supposed, but the winged insects frequently rest and hide in vegeta- 


tion. The different species of mosquitoes not only differ markedly in 
their habits, but differ considerably in the character of their breeding 
places. The domestic species, such as the yellow fever mosquito and 
Culex pun gens, may be found breeding in any collection of water 
in or about houses. Thus, they have been found in discarded tin cans, 
bottles, and broken crockery on the garbage heap ; in buckets, tubs, bar- 
rels, cisterns, and wells ; in baptismal fonts ; in flower pots and sagging 
roof gutters; in street and roadside puddles, gutters, and ditches; in 
cesspools and sewers. 

The semi-domestic mosquitoes, to which the malarial-bearing insects 
belong, may occasionally be found breeding in tin cans, barrels, hoof 
prints, post holes, and hollows in trees or tree stumps, but they usually 
prefer grass-bordered pools, slowly flowing ditches, the margins of lakes 
and streams, even such as are stocked with fish, provided the margins 
are shallow or are more or less choked Avith reeds and water plants so 
that the fish cannot reach them. The sylvan or wild mosquitoes select 
breeding places of mu£h the same character as do the semi-domestic 
species, with which they are not infrequently found associated, except 
that such breeding places are more or less remote from human habita- 
tions, in woods, swamps, and fresh or salt (brackish) coastal marshes. 

Male mosquitoes are vegetarians. The females of many spe- 
cies have developed a taste for blood, and, indeed, blood has become 
indispensable to nearly all for the full development of their eggs. This 
is the case with Stegomijia calopus. Eemembering how all-important 
the generative instinct is, we can now well understand why the yellow 
fever mosquito, for example, will, when disturbed, return again and 
again in an endeavor to obtain her fill of this life-giving iluid. 

The mosquito lays her eggs upon the surface of the water, and 
these, depending upon the species, either fioat separately on their sides 
(Stegomyia calopus and Anopheles), or adhere together in irregular, 
raft-like masses (Culex). In a day or two, under ordinary conditions, 
the eggs hatch out into larvse or "wiggle-tails." Although the larva 
is an aquatic animal, it is a true air-breather. The larva of Anopheles 
ordinarily rests and feeds at the surface, where it lies in an almost 
horizontal position, its tail and dorsal bristles touching the surface 
film, while it breathes through a breathing siphon, which is very short 
and insignificant in appearance. 

The larvse of the other species move about more or less, actively 
searching for food, but at intervals of a minute or two they may be 
seen to come to the surface for air, where they hang, head down, at- 
tached by their more or less prominent conical breathing tubes to the 
surface film. The mosquito remains in the larval stage about a week 
and is then transformed into a comma-shaped creature known as the 


The pupa has no mouth and does not feed. It remains quietly at 
the surface except when disturbed. It breathes through a pair of trum- 
pet-shaped tubes, whicli project from the dorsum of the thorax. The 
pupal stage usually lasts two or three days, and is terminated by the 
emergence of the adult winged insect (imago) from its pupal case 
through a rent in the region of the breathing tubes. 

The time from the laying of the egg to the winged insect may, there- 
fore, be as short as nine days. The time depends upon the tempera- 
ture and the abundance of the food supply. Warmth favors and cold 
retards; therefore, mosquitoes are most abundant during the summer, 
late spring, and early fall months in our climate. In the tropics the 
wild species become more al)undant during the wet season. 

The way in which mosquitoes manage to pass through the rigors of 
the winter probably varies with the different species. Some, like the 
malarial Anopheles, hide in sheltered cellars or dark nooks, or hibernate 
in other out-of-the-way places. Other species survive through the power 
of the larva or egg to resist cold, for the larvae or eggs of some species 
will hatch even after they have been frozen. 


The life of a mosquito may be divided into an aquatic and an aerial 
stage, the former including the egg, larva, and pupa, and the latter 
the adult winged insect. Accordingly, the measures aimed at the de- 
struction of the mosquito naturally fall into two classes: (a) those di- 
rected against the larva and pupa — the aquatic stages — and (b) those 
directed against the winged insect. 

For the extermination of mosquitoes the most effective measures 
are those which aim to destroy their breeding places, and thus prevent 
their multiplication. For the best results both individual and com- 
munal effort are necessary, but the importance of individual effort alone 
cannot be too much emphasized. The individual, b}' attacking the prob- 
lem on his own premises, grounds, or estate, can not only do much to 
rid his own immediate neighborhood of mosquitoes, and thereby in- 
crease his own comfort and guard against disease, but the example thus 
set will perhaps stimulate his less enterprising neighbor. 

To insure success it is important to know the habits and breeding 
places of the particular species that it is desired to suppress. 

Natural Breeding Places. — Xatural collections of water which may 
serve as breeding places are best dealt with by filling in or by draining. 
In this way they are disposed of once for all. For filling, inorganic 
refuse, such as cinders and ashes, may be employed, or sufficient earth 
may be dug from a nearby knoll or hill, care being observed that in so 
doing a depression capable of holding w^ater is not made. Low marshy 


lands adjacent to rivers, lakes, or the sea may be filled by pumping silt 
or sand. 

When filling is not practicable, good and permanent results may 
be obtained by drainage. As a rule, the draining of ponds, pools, or 
marshes is the simpler and cheaper method. By the draining of marshes 
is meant the draining of the pools of stagnant water, or in the case of 
coastal marshes the draining of the stagnant fishless pools that are be- 
yond the reach of the ordinary tides; it does not necessarily include the 
draining of the water-soaked soil itself. The underdraining of wide 
acreages of our arable land in the Middle West has been very effective 
in suppressing the malarial mosquito. Marshy lands may be drained 
simply by means of ditches. These must be dug of sufficient depth to 
completel}" empty the joools under treatment and have sufficient fall to 
prevent stagnation in the course of the ditch itself. Where a sufficient 
fall is not obtainable fishless pools may be connected with those con- 
taining fish or with a neighboring stream, so that the fish may freely 
enter. Mosquito breeding places in the pools in coastal marshes may 
be suppressed by connecting them with tide water, so that they may 
be freely scoured by the daily tides. Ditches should have straight sides 
and must be inspected at frequent intervals, and care must be taken to 
see that they do not become choked. 

Fish are among the most effective of the natural enemies of the 
mosquito. The fish may be admitted to ponds and pools in the man- 
ner just described, or the ponds, pools, ornamental lakes, and fountains 
may be directly stocked with minnows or gold fish. The margins of 
pools, rivers, and other bodies of water must be kept free of reeds 
and water plants, so as to permit the fish to reach the edges — a favorite 
breeding place for mosquitoes. One of the very best means of clear- 
ing the land of the numerous small natural collections of water is to 
place it under cultivation. 

When radical measures, such as filling in or draining, are not prac- 
ticable, resort may then be had to coal oil. Coal oil upon the surface 
of the water acts mainly by suffocating the larvge and pupse. A light 
qualit}^ of oil should be used, and it may be poured upon the surface 
from an ordinary sprinkling pot, or the surface may be sprayed with 
a hose. Along the banks of ponds, lakes, and slowly moving streams 
with shallow margins containing vegetation, which offer favorite breed- 
ing places for the mosquito, the oil may be applied with a mop. This 
practice is laborious, but effective. Sufficient oil should be used to 
cover the entire surface with a thin film. As the oil is volatile, it may 
disappear within a few days. Furthermore, the film, which should be 
intact to be effective, may be broken by winds. A strong wind will blow 
all of the oil to one side, thereby entirely defeating the object desired. 
It is, therefore, imj)ortant to repeat the oiling regularly at intervals 


of not more than one week, and as often in addition as necessary. 
Oiling, though fairly effective when properly carried out, is only a tem- 
porary expedient, and in the end is rather expensive. (See also page 206.) 

No body of water is too small for a mosquito nursery. They breed 
in puddles by the roadside; in water that accumulates in furrows in 
gardens or fields, especially in clayey soil ; in street gutters and house 
gutters; in holes in rocks; in hollows in trees, and anywhere that half 
a pint of water is allowed to stand. 

Artificial Breeding Places. — The permanent elimination of artificial 
breeding ]*lace.s for iiiu.<(]uitoes in a city depends first of all upon provid- 
ing a good quality and sufficient quantity of portable water by means of a 
modern closed system. This will permanently do away with the neces- 
sity of cisterns, barrels, and tubs for the storage of water about the 
premises. When domestic storage is a necessity, care must be taken to 
prevent the mosquito from gaining access to the water. The water bar- 
rels should be provided with tightly fitting covers. Burlap, sheeting, or 
several thicknesses of cheese-cloth, or, better, wire acreening held in 
place by a well-fitting hoop, serve this purpose very well. Wooden 
covers are unsatisfactory, for they rarely fit accurately enough to keep 
out the mosquito, and this defect is enhanced by the warping of the 
wood, which usually makes an old cover worse than useless. More 
satisfactory than the wooden cover is one made of light galvanized 
sheet iron, the central portion of which may "be made of wire gauze. The 
rim of the barrel should be trimmed to remove any irregularities that 
might prevent the cover from fitting evenly all around. Whatever the 
form of the cover employed, it should not be removed except for cleaning 
or refilling the barrel. The water should be drawn from a spigot. 
Where the water is very turbid and must undergo sedimentation before 
being used, several barrels should be provided for its storage and the 
water used from each barrel in turn. In such a case the spigot should 
be placed about a foot from the bottom, so that the sediment need not 
be disturbed as the water is drawn off for use. Wells should be pro- 
vided with tight covers and the water drawn by pumps. 

Cisterns and tanks should also be provided with accurately fitting 
covers, and should be inspected frequently for seams and cracks result- 
ing from warping and shrinking of the wood. To guard against this 
loophole, wire gauze should be used to screen the joint between the tank 
and its cover. The gauze should include about one foot of the tank 
and overlap well upon the cover. The inlet to the tank or cistern 
should be provided with a cap of copper meshed wire gauze which may 
be protected by another and coarser meshed cap of stout wire, to pre- 
vent its choking with leaves, etc. As an additional precaution, the in- 
let pipe should be long and extend well below the water level. In cases 
of emergency, as in times of epidemics of yellow fever or dengue, where 


the permanent measures for preventing mosqnito breeding have been 
neglected, the surface of the water in barrels, tanks, and cisterns may 
be , covered with some neutral non-volatile oil which does not impart a 
taste to the water. 

Cesspools and privy vaults should be done aAvay with and replaced 
with dry earth closets or a water carriage cistern. Where this has not 
been done they may be frequently and copiously oiled. 

Among the artificial breeding places for mosquitoes may be men- 
tioned chicken-pens in poultry yards; water cups on the frames of 
grindstones; baptismal fonts; tin cans or broken bottles in back yards; 
the catch basins of sewers; the water that stands in sagging house gut- 
ters; tlower-pots, and similar places. 

Screening. — Mosquito screens are the obvious and most effective 
single measure for personal prophylaxis where disease-carrying mosqui- 
toes exist. In order to be effective the screening must be intelligently 
carried out with careful attention to details. The screen itself must 
be sufficiently close to keep out the mosquitoes. Some of them are able 
to squeeze through surprisingly narrow chinks. I was able to demon- 
strate, in the experimental work at Vera Cruz, that the stegomyia mos- 
quito can pass a metal wire screen containing 16 strands or 15 meshes to 
the inch, but cannot pass one containing 20 strands or 19 meshes to the 
inch. When the screen consists of a fabric which is apt to pull out of 
shape so that some of the meshes are larger than others, it is advisable 
to use a net woven closer than 20 strands to the inch. Experience in 
malarial and yellow fever districts has taught this lesson, so that it is 
customary in those countries to use a rather closely woven material re- 
sembling nainsook. Metal screens made of iron wire are cheapest only 
when first cost is considered. They hardly last a season unless painted, 
in which case the size of the mesh is considerably reduced and inter- 
feres with ventilation, a serious objection in hot weather or a tropical 
climate. Mesh made of galvanized iron wire has a greater durability. 
Screens made of brass or bronze are expensive, but cheap in the long 
run, as they are found to last almost indefinitely. 

The screening should include the entire house, or at least those 
parts that are occupied. In the tropics it is better to screen the gal- 
leries than each individual window. In any case, frequent and repeated 
inspection should be made to discover breaks in the screen or openings 
due to warping of the woodwork. In screening care must be exercised 
not to overlook fireplaces, ventilators, and other openings. The door 
should be guarded by a screened vestibule of such a depth as to make 
it impossible for a person to hold both doors open at the same time. 
The screen door should open outward and, if possible, should be exposed 
to the direct sunlight during the day without vines or nearby vegeta- 
tion of any kind to protect and lodge the mosquitoes. During the night 

206 L\Sl-:("r-lU)lJ.\K DI.SEASKS 

the floor sliould not bo in an artificial li<rht, which attracts many mos- 
quitoes. An electric fan directed outward is a very cjcod device to pre- 
vent mosquitoes flyin^^ through the doorway. In ailditinn. a whisk- 
broom or feather duster should hang in the vestil)iile to brush olf the 
insects that may rest upon the clothing. A screened house is safe only 
to careful and intelligent people. 

In addition to screening the house, mosquito bars over the bed will 
be found necessary in mosquito-infected places. It is best to suspend the 
mosquito bar from the ceiling and carefully gather the l)ottom together 
so as to keep the insects out during the day time. At night the bar 
should be carefully tucked in around the bed so as to leave no openings. 
Mosquitoes have no trouble in i)iting through the meshes of the Inir, 
provided a restless sleeper comes close enough to it. 

Persons who are required to go out at night in a malarious district, 
or who must expose themselves during yellow fever times, may screen 
themselves effectively with a veil of mosquito netting hanging from a 
broad-brimmed hat to the shoulders and chest. The hands and wrists 
may be protected witli gloves, and the ankles w'ith leggings or other 
suitaljlo mechanical device. 

Miscellaneous Measures. — Spirits of camphor, oil of pennyroyal, and 
other volatile substances, such as oil of peppermint, lemon juice, or 
vinegar. n;bl)ed upon the face and hands, or a few drops on the pillow 
at night, will keep mosquitoes away only for a time. Oil of citronella 
is one of the best known sul)stances to be used in this way. Ordinarily 
a few drops on a bath towel hung over the head of the bed will keep 
the common house mosquitoes away. When they are very abundant and 
persist, a few drops rubbed on the face and hands will suffice. All these 
substances soon lose their efficiency ; none of them last until morning. 

In Panama a larvicide is being used which is made as follows: 150 
gallons of carbolic acid is heated in a tank to a temperature of 212° F., 
then 150 pounds of powdered or finely broken resin is poured in. The 
mixture is kept at a temperature of 212° F. Thirty pounds of caustic 
soda is then added, and the solution is kept at the same temperature 
until a perfectly dark emulsion without sediment is formed. The mix- 
ture is thoroughly stirred from the time the resin is used until the end. 
One part of this emulsion to 10,000 parts of water is said to kill Ano- 
pheles larvae in less than half an hour, while 1 part to 5.000 parts of 
water will kill them in from 5 to 10 minutes. 

The Panama larvicide is mixed with 5 parts of water and sprayed 
upon pools or along the banks of streams. This larvicide added to 5 
parts of crude petroleum favors its spread upon the surface of the w-ater. 
A good method is to place the mixture in a barrel and permit it to 
drip i;pon the surface of the stream or pond to be treated. 

Other larvicides that may be used in water not used for drinking 


purposes are: sulphuric, hydrochloric, and other acids, potassium per- 
manganate, sulphate of copper, sulphate of iron, bichlorid of mercury, 
carbolic acid, anilin products, or coal tar. They must be used in rela- 
tively large amounts to be effective, and frequently renewed according 
to circumstances. 

The diseases known to be conveyed by mosquitoes are : malaria 

{Anoplieles spp.), yellow fever {Stegomyia calopus), filariasis {Culex 
fatigans), dengue {Culex fatigans), and doubtless other infections. 


Malaria is one of the most prevalent of all preventable diseases ; it is 
the scourge of the tropics. The cause of this infection was one of the 
first to be discovered (Laveran, 1880), and its mode of transmission 
was one of the most brilliant discoveries in sanitary science (Eoss, 
1895). Despite the fact that we have more exact knowledge of malaria, 
considering the difficulties of the subject, than perhaps any other dis- 
ease, despite the fact that we have accurate means of diagnosis and a 
ready cure, and despite the fact that we have assured measures of pre- 
vention, malaria counts its victims by the hundreds of thousands annu- 
ally. In geographic distribution malaria extends from the Arctic circle 
to the Equator, but becomes more virulent the warmer the climate. 

At least three separate malarial parasites of man are known, namely : 
(1) Plasmodium malarice (Laveran), quartan fever; (2) Plasmodium 
vivax (G-rassi and Filetti), tertian fever; and (3) Plasmodium falci- 
parum (Welch), estivoautumnal or tropical malaria. These are closely 
allied hematocytozoa or blood parasites. They produce diseases with 
well-defined clinical differences, but having the same etiology and mode 
of transference, so that, as far as prevention is concerned, they may 
be regarded as one infection. 

Many species of animals have a malarial-like infection closely re- 
sembling malaria in man; for example, Texas fever of cattle, piroplas- 
mosis of dogs and sheep, proteosoma of birds, etc. So far as is known, 
no other animal than the Anopheles mosquito is subject to the malarial 
parasites pathogenic for man. Both man and the mosquito are neces- 
sary to complete the life cycle of the plasmodium. Man is the inter- 
mediate host harboring the asexual phase, and the mosquito is the defi- 
nitive host harboring the sexual phase of the life cycle of the plas- 

Mosquito Transmission. — It is now definitely known that in nature 
malaria is transmitted only by the sting of the Anopheles mosquito.^ 
Experimentally, the infection may be transferred by injecting blood 

^ The genus Anopheles has recently been divided into several genera. 


(containiniT the parasites) of one person into the system of another. 
Nearly 2,000 years ago Varro and ColunibeUa mentioned the possibility 
that the disease was transmitted by mosquitoes. In Africa some savage 
tribes call malaria the "mosquito disease." In 1848 Nott, of New Or- 
leans, considered the matter proven from biological analogies. In 1883 
King, of Washington, vigorously advocated the mosquito theory based 
upon philosophical deductions but no proof. In 1884 Laveran suggested 
mosquito transmission as probable. In 1894 Manson elaborated the 
mosquito theory and inspired Eoss, of the Indian Army Medical Service, 
who in 1895 demonstrated that the crescents of estivoautumnal malaria 
underwent changes in the mosquito. In 189G Bignanii advocated the 
theory and compan'd it to the transmission of Texas fever by the tick. 
In 1897 Ross published further convincing observations upon the de- 
velopment of the estivoautumnal parasite in the mosquito. In 1898 !Mc- 
Collum observed an important missing link in the life cycle by observ- 
ing the tlagellum of the microgametocyte (male) fertilize the macro- 
gametocyte (female) with the formation of the vermicule. These ob- 
servations were made upon Halteridum or malaria of birds; later he saw 
the same phenomenon in estivoautumnal malaria. The life cycle of the 
malarial parasite has been confirmed l\v Daniels, Koch, Grassi, Big- 
nami, Celli, Manneberg, Schaudinn, and others. 

Further evidence that malaria is transmitted by the mosquito was 
furnished by Sambon and Low, of the London School of Tropical Medi- 
cine, and Dr. Terzi, who lived during the three most malarial months of 
1900 in Ostia, a very malarial locality of the Roman Campagna. These 
observers escaped infection simply by keeping within their well-screened 
hut from before sundown until after sunrise. The final proof was fur- 
nished in 1900 by Dr. P. Thurber Manson and Mv. George Warren, who 
were bitten by infected mosquitoes forwarded from Italy in cages to 

The Malarial Mosquito. — Of the fifty or more species of the genus 
Anopheles sixteen are known to transmit malaria. In Europe Anopheles 
maculipennis, in tropical America A. argyrotarsus or albipes, in tem- 
perate America, A. quadrimaculatus, which is probably the same as A. 
■maculipennis, in India A. sinensis, in Africa A. costalis, are the chief 

The Anopheles mosquitoes are brownish and rather large. They may 
be distinguished by the fact that the palpi in both the male and the 
female are at least as long as the proboscis. Only the female transmits 
the infection. It sits more or less at right angles upon the wall, the 
head, thorax, and abdomen being in a straight line. Contrary to the 
yellow fever mosquito, the malarial mosquito is nocturnal in its habits 
and breeds chiefly in the open ponds, puddles, and natural collections 
of water in the woods, fields, and swamps. 



Fig. 19. — Anopheles Punctipenis. 

The mosquito becomes infected upon drinking the blood containing 
the micro-. and macrogametocytes. It requires about twelve days before 
the sporozoites appear in the 
salivary glands of the insect. It 
cannot, therefore, transmit the 
infection to another person until 
the lapse of this extrinsic period 
of incubation. The infected mos- 
quito may live a long time and 
infect more than one person suc- 
cessively. The malarial parasite 
seems to be a harmless sapro- 
phyte for the mosquito. 

Immunity. — A person who 
once has had malaria is more 
apt to have subsequent attacks. 
Ordinarily there is an increased 
susceptibility rather than an im- 
munity. However, repeated in- 
fections, especially during early 
life, leave a very pronounced re- 
sistance. In malarious regions many children carry the parasites in 
their circulating blood without any manifestations of the disease. 
These carriers are important factors in spreading the infection in en- 
demic areas, and must be taken into account in preventive measures. 

There is no true racial immunity in this disease. Occasionally a 
congenital immunity seems to be transmitted; this must be rare. Prac- 
tically all persons who receive the infection for the first time are sus- 
ceptible. The freedom from malaria which some persons seem to enjoy 
may be accounted for partly by the fact that mosquitoes seldom bite 
such persons. It is well known that on account of the odors, or what 
not, mosquitoes do not bother certain individuals. No doubt the in- 
fection of a small number of parasites is often overcome largely through 
a vigorous phagocytosis. 

Individual resistance varies in different individuals and in the same 
individual at different times. The parasite may remain latent in the 
spleen and other organs for years. Exposure, overeating, fasting, over- 
work, or worry, or anything that lowers the vitality of such individuals 
predisposes to an attack of malaria. The disease often breaks out in 
persons in good health leaving a malarial region for a health resort, 
whether mountain or seashore. I was enabled to confirm this observa- 
tion upon the returning transports from Cuba following the Spanish- 
American war, when many cases of malaria broke out among the troops 
previously in good health upon reaching the cold winds about Cape 


Hatteras. Personal prophylaxis, therefore, involves careful attention to 
personal hygiene. 

Prevention. — The successful suppression of malaria requires a com- 
bined attack upon the mosquito and the parasite in the human host. 
Ultimate success rests upon the suppression of the mosquito. This, 
however, is a difficult and expensive undertaking in the case of the 
Anopheles. Immediate relief is most quickly gained by measures directed 
against the infection in man. Screening and quinin prophylaxis, while 
practical, are only temporary measures; 

Measures Directed Against the Mosquito. — If the breeding of 
the Anopheles mosquito could be stopped malaria would cease. Mosquito 
suppression is fundamental and radical. The best way to abolish the 
breeding places of malaria mosquitoes is to fill up low places or to dry 
the surface of the land with drains. These two measures hold first 
place as permanent work. The underdraining of large areas of our 
arable land of the Middle West with tiled drain has been very effective 
in supjjressing malaria. Open ditches properly constructed and cared 
for are likewise effective. In the tropics the ditches should be lined 
with cement, on account of the lux:uriant vegetation which soon interferes 
with their efficiency or may actually convert them into breeding places. 
The open ditches are much the cheapest in first cost, but not when 
maintenance is reckoned. The draining of swampy lands is an engineer- 
ing problem in which the economic factor looms large. One of the very 
best means of destroying the breeding places of the malaria mosquito 
is to clear the land and to keep it in cultivation. 

"When drainage is not practical, the number of mosquitoes may be 
kept down by introducing fish into the pools, streams, ditches, and 
other collections of water. Upon limited water surfaces the larvae may 
be killed with a film of coal oil. 

Large open spaces cause the destruction of a number of mosquitoes, 
as they cannot live long in the hot sun ; therefore, clearing the brush 
and high grass, which furnish shelter to the insects, aids in keeping away 
wild mosquitoes around dwelling houses. 

The use of screens and culicides has already been referred to. 

Personal Prophylaxis. — Persons visiting or residing in a malari- 
ous region should be particularly careful not to expose themselves at 
night time. The experience of Sambon and Low on the Roman Cam- 
pagna is instructive and should be imitated. The location of the resi- 
dence is important. In a city it should be a reasonably safe distance 
from the native quarter, because the infection is there most concentrated. 
The dwelling should, if possible, face the trade winds. A row of tall 
trees will partly screen the house from the swamp, but the trees must 
not be too close, else they will furnish shelter for the insects. The 
house should be on high land if practicable, as it is an old observation 


that the malarial mosquito does not fly high. People living upon the 
second floor are less apt to contract the infection than those who sleep 
on the ground floor. If it is necessary to go out in the night time, one 
may protect himself by the use of gloves and mosquito netting hang- 
ing from the helmet to the shoulders. Care must be taken to guard 
the ankles against mosquito bites. As all these measures require much 
time and attention to details, they are usually not sufficient in actual 
practice. Therefore, quinin prophylaxis is much used. 

QuiNiN Prophylaxis. — Theoretically the administration of quinin 
to healthy individuals for the prevention of malaria is not an ideal 
method of prophylaxis, for it does not prevent infection, but only de- 
stroys the parasites in the blood during the period of incubation. It 
should be remembered that quinin kills only the young and tender forms 
of the Plasmodium, and has no influence upon the crescents. Quinin 
prophylaxis is indicated in proportion to the difficulty of pursuing more 
permanent methods. It is especially valuable where screens and bars are 
not available, as in camping, marching, traveling, or where the occupa- 
tion takes one out at night. When residents of non-malarial countries 
go into malarial localities, especiallv in the rural districts, for short 
periods of time, quinin is a valuable preventive. 

To be effective as a preventive of malaria, quinin must be taken in 
sufficient doses during the entire malarial season. The expense of pub- 
lic prophylaxis with quinin on a large scale is enormous; in fact, in 
some instances prohibitive. The daily ingestion of 2.5 grains would 
require the annual use of no less than 59.4 tons per million people. 
The size of the dose and the interval at which the prophylactic is ad- 
ministered are of the utmost importance. Koch advised one gram of 
quinin every sixth or seventh day, or every seventh and eighth day, or 
eighth and ninth, or ninth and tenth day, according to the danger of 
the infection. This manifestly leaves several intervening days in which 
there is no quinin in the circulation. In localities, therefore, where 
estivoautumnal malaria is prevalent, a shorter interval should be pre- 
ferred on account of the shorter period of incubation of this form of 

Ziemann gives a gram of quinin sulphate every four days. The al- 
kaloid is administered in solution with 5 drops of hydrochloric acid 
early in the morning or about one and one-half to two hours after a 
meal. A convenient rule is to give a dose on the first of the month 
and thereafter on each day of the month divisible by 4. By this method 
the alkaloid is probably constantly in the circulating blood. 

Plehn advises one-half a gram of quinin every fifth evening. 

The administration of small doses of quinin daily is the oldest method 
of giving quinin as a prophylactic. From II/2 to 6 grains have been given 
daily. In Italy 0.04 gram (about 2-3 grain) daily is the universally 


adopted dose, and accomplishes good results. The Italian government 
undertakes the sale of quinin at a low price. This is a beneficent public 
health measure comparable to the free distribution of antitoxin and vac- 
cine virus. 

On the Isthmus of Panama good results have been obtained by the 
use of moderate doses, 3 to 6 grains per day. When the disease in- 
creases in prevalence or virulence the amount is raised to 8 or 10 grains 
per day, then dropping off to 4 or 5. 

The particular metliod of election in giving quinin prophylaxis should 
be chosen according to the experience of the region. 

An objection to the use of quinin as a prophylactic has recently been 
raised by Stitt, who claims that the malarial parasites gradually become 
immune to the effects of the alkaloid, and that when the disease subse- 
quently breaks out in one who has used quinin as a prophylactic it is 
not readily amenable to treatment. Ehrlich has shown experimentally 
that trypanosomes may be immunized in this sense to trypanrot, and 
that other microparasites belonging to the animal kingdom may similarly 
be accustomed to unusual amounts of substances ordinarily very toxic. 

Quinin prophylaxis has advantages that commend it as a prompt and 
practical measure. It is at best, however, only tentative, and does not 
take the place of mosquito suppression. 


The prevention of yellow fever rests entirely upon the fact that it 
is communicated through the bite of an infected mosquito — the Stego- 
myia calopus} The mosquito becomes infected by sucking the blood of 
yellow fever patients during the first three days of the fever. All the 
experimental evidence thus far shows that the infection is absent from 
the blood after the third day, and that mosquitoes do not become in- 
fective after this period. The importance of this fact in preventing the 
spread of the disease is evident. The mosquito, after drinking the in- 
fected blood, is not able to transfer the infection to another person until 
about twelve days- have elapsed; that is, it requires about twelve days 
for the yellow fever parasite, whatever it may be, to undergo its cycle 
of development in the mosquito. The mosquito once infected remains 
so during the rest of its life, which may be many months. Only the 
female mosquito transmits the infection ; the male Stegomyia calopus is 
a vegetarian; its proboscis is too soft to penetrate the skin. A single 

* This mosquito was first called Culex fasciatus, which was changed to 
Stegomyia fasciatus, and then to Stegomyia calopus, and recently expressed as 
A'edes calopus by Coquillett. 

■ This constitutes the extrinsic period of incubation, in contradistinction to 
the intrinsic period of incubation, that is, the time between the mosquito bite 
and the onset of symptoms, which is from 2 to 5 and sometimes 6 days in this 


sting of a single infected mosquito is sufQeient to produce the disease. 
An infected mosquito may infect more than one person at different 

Tlie prevention and control of yellow fever are based upon a series 
of epoch-making investigations and discoveries (1900-1902) by a com- 
mission composed of Walter Eeed, James Carrol;, Aristides Agramonte, 
and Jesse W. Lazear, medical officers of the United States army. These 
experiments have been fully confirmed, and in some respects amplified, 
by independent workers, namely, Guiteras of Cuba (1901) ; Barreto, de 
Barros, and Eodrigues, of Brazil (1903) ; Eoss (1902) ; Parker, Beyer, 
and Pothier (1903) ; Eosenau, Parker, Francis, and Beyer (1904) ; 
Eosenau and Goldberger (1906), of America; Marchoux, Salimbeni, and 
Simond (1903); Marchoux and Simond (1906), of France; and Otto 
and Neumann (1905), of Germany. 

The cause of yellow fever is unknown. The virus is ultramicroscopic, 
that is, passes the close-grained pores of the finest porcelain filter. 
While in nature the disease is transmitted only through the bite of an 
infected Stegomyia, the disease may be transferred experimentally by 
taking some of the blood from a patient during the first three days of 
the fever and injecting it into a susceptible individual. So far as is 
known, yellow fever is peculiar to man, for all other animals tested have 
failed to react. At one time it was generally believed that yellow fever 
infection was conveyed by fomites. This has been disproved, and we now 
know that there is no danger from soiled clothing or other inanimate 
things, even though stained with the black vomit and other discharges. 

The diagnosis of yellow fever rests upon clinical evidence and is fre- 
quently difficult to make, especially in the early stages. It is, therefore, 
important to screen all cases' of fever in a yellow fever campaign until 
the nature of the illness is established. 

Immunity. — There is no natural immunity to yellow fever. All per- 
sons receiving the infection for the first time seem to be susceptible. 
Contrary to the usual statement, there is no racial immunity in this dis- 
ease, for negroes, Chinese, Indians, and other races take the disease. 
One attack of yellow fever affords protection against a subsequent attack. 
The acquired immunity in this disease is one of the strongest known 
and lasts throughout the lifetime of the individual. Two attacks of 
yellow fever are almost unknown. I reported a supposed instance in a 
Spaniard in Havana, but the diagnosis of tlie first attack was not con- 

In endemic areas children may have yellow fever, which leaves them 
immune for life. The disease often runs a mild and unrecognized course 
in children, and this fact explains the supposed natural immunity of 
natives in endemic foci. 

The Yellow Fever Mosquito. — The yellow fever mosquito has a wide 



distribution ranging from 38 degrees south to 38 degrees north latitude. 
They are found in the East and West Indies. China, Sumatra, Java. In- 
dia, Philippine Islands, Japan, Hawaiian Islands, in tlic SDutlnM-n part of 
Italy, Africa. Spain, South America, etc. They usually ])refer the low- 
lands. I have found them 
as far up llie mountains 
as Orizaba in Mexico, 4,- 
200 feet above sea level. 
In tlie United States they 
are very prevalent south 
of the Potomac along the 
gulf coast, but are absent 
or rare in the higher 
elevations of Georgia or 
A 1 a b a ni a , which are, 
therefore, non-infectable 

The yellow fever mos- 
quito is a domestic in- 
sect. It breeds by pref- 
erence in any standing 
water about the house- 
hold, such as cisterns, 
rain barrels, or any col- 
lection of water in 
buckets, bottles, old cans, 
etc. The yellow fever 
mosquito does not breed 
in the fields, woods, and 
swamps, which are the 
favorite resorts of the 
malarial mosquito. The 
Stegomyia mosquitoes do not fly far of their own volition, but sliow a 
cat-like tendency to remain about their place of birth or adoption. All 
these facts have an evident bearing upon preventive measures. A 
thorough knowledge of the biology of the mosquito is essential to the 
success of a yellow fever campaign. 

It is important to remember that the yellow fever mosquito is chietly 
active during the day time. It cannot, however, distinguish between 
artificial light and sunlight. I have watched Stegomyia mosquitoes bite 
me by electric light at eleven o'clock at night. However, as a rule, 
they rest at night, which, therefore, diminishes the risk of exposure 
at that time. The Stegomyia mosquito, however, cannot survive for 
long in the direct rays of a tropical sun. There is, therefore, little 

Fig. 20. — Stegomyia Calopus (female). 



danger in visiting a community where yellow fever is epidemic dur- 
ing the day time, provided the person keeps out of houses. The ex- 
periences during the last yellow fever epidemic at New Orleans, 1905, 
showed that the radius of activity of an infected Stegomyia is con- 
tracted. It may possibly at times fly across the street, but it is evident 
that it neither flies far nor is it ordinarily transported to any great dis- 
tance on railroad cars, although it may be carried over seas on ships. 

The yellow fever mosquito 
may pass a screen composed 
of 16 strands or 15 meshes to 
the inch, but cannot pass one 
containing 20 meshes or 19 
strands to the inch. Effective 
screens must, therefore, be at 
least this fine. 

Stegomyia calopus is a 
grayish mosquito of average 
size with beautiful glistening 
silver-white markings. These 
markings are lyre-shaped on 
the back of the thorax; silver- 
white spots are seen on the 
side of the thorax. White lines 
are apparent at each tarsal 
joint and also on the palpi; 

the scutellum is white. In the female the palpi are much shorter than 
the proboscis, which at once distinguishes it from Anopheles. 

Egg. — The female lays her eggs on the surface of the water or just 
above the water line. The eggs do not adhere to one another, and hence 
do not form the compact boat-shaped mass characteristic of the culex, 
but float on their sides more or less singly. At the moment of laying 
the eggs are a cream color, but rapidly become jet black. They are 
somewhat cigar-shaped, and measure on the average about 0.55 mm. in 
length and 0.16 mm. in width at the broadest part. The eggs show 
marked powers of resistance to unfavorable influences. They may be 
kept dry for six and one-half months, and still retain their vitality, and 
hatch out when put back into the water. Freezing does not kill them. 
The egg probably plays an important role in the hibernation of the 
yellow fever- mosquito. The winged insect may also survive a short 
winter. Under the most favorable conditions as to temperature (30° C.) 
Stegomyia eggs hatch out in about 36 hours after they are laid. Under 
20° C. they will not hatch at all. 

Larva. — The egg hatches the larva ("wiggle-tail"), which has a 
black barrel-shaped respiratory siphon. This distinguishes it from Culex 

Fig. 21. — Head of Stegomyia Calopus (male). 



Fig. 22. — Eggs of Stegomtia Calopus. 

pxpiens, its common mess mate, in which the air tube is brown, longer, 
and more slender. Although the larva lives in the water, it is strictly 
an air-breather and must come to the surface for air. It thrusts its 
breathing tube up into the surface film and remains suspended, head 
down, at an angle of somewhat less than -15 degrees, which distinguishes 
it from Anopheles larvae, which lie horizontal. A film of oil on the 
surface of the water is sufficient to obstruct the air tube and thus cause 

Fig. 23. — Larva of Stegomtta Calopus. 
Respiratory Syphon of Culex to the Right. 



the death of the larva by suffocation. The larva is very timid, so that 
a slight jar or agitation or a sudden shadow will cause it to wriggle 
rapidly to the bottom, where, indeed, it may very commonly be observed 
to feed. The duration of the larval stage is never less than 6 to 7 
days, and depends upon the food supply and temperature. Under fa- 
vorable conditions it may be prolonged for weeks. Freezing for short 
periods does not appear to injure it. 

Fig. 24. — Pupa of Stegomtia Calopus. 

Pupa. — The larva changes into the pupa. The pupa is not provided 
with a mouth and does not feed. It is an air-breather and spends most 
of its time at the surface of the water. The pupal stage lasts at least 
36 hours, during which time metamorphosis occurs into the imago or 
perfect winged insect. 

Imago. — Under the most favorable conditions it is at least 9 days 
from the time the Stegomyia lays its egg to the appearance of the 
imago. Under natural conditions the length of life of the adult female 
probably varies greatly. Guiteras succeeded in keeping a presumably 
infected one alive for 154 days during the fall and winter temperature 
in Havana. Deprived of water, it does not usually survive longer than 
3I/2 to 4 days, and only very exceptionally 5 days. This fact has a 
bearing on the possibility of transporting the mosquito in band-boxes, 
trunks, and other containers. 

"Aerial" Conveyance, — It is notorious that yellow fever is usually 
ponveyed but a short distance "^aerially" — perhaps across the street, or. 


more often, to a neighboring house in the rear. This represents a dis- 
tance of some 75 yards, which is about as far as we may expect it to 
be thus conveyed, from our knowledge of the habits and flight of the 
Stegomyia mosquito. The longest distance recorded in recent years of 
aerial conveyance is one of 225 meters (Melier) and one of 456 feet 
(Carter). These are entirely exceptional. My experience in the deten- 
tion of hundreds of susceptible immigrants in quarantine for days in 
Havana harbor showed that infected Stegomyiae do not travel a short 
distance across the water. Tliis observation is in confirmation of others, 
that vessels moored within 1,200 feet of the shore are entirely safe so 
far as yellow fever is concerned, provided, of course, personal intercourse 
is interdicted or supervised. 

Prevention. — The prevention or suppression of yellow fever may be 
attacked in either one of its two hosts, man or insect. If every person 
developing yellow fever were immediately isolated from the Stegomyia 
mosquito, the disease would inevitably cease. The elimination of the 
Stegomyia mosquito would give the same happy result. Usually both 
methods of attack are employed. It would seem easier to control the 
human hOst simply by screening during the first three or four days 
of the fever. Practically this method has been found insufficient, be- 
cause the disease is difficult to diagnose in the early stage, and the 
mild cases escape attention. The essence of yellow fever prevention, 
therefore, consists in : ( 1 ) screening cases of yellow fever and all sus- 
pected cases of yellow fever; (2) destruction of infected insects; (3) 
the suppression of stegomyiae through the control of their breeding 
places. It was a combination of these three methods which was first so 
brilliantly carried out by Gorgas in Havana in 1901, and later in 
Panama ; by White in Xew Orleans, 1905 ; by Liceaga for Vera Cruz, 
and recently by Oswaldo Cruz in Eio de Janeiro, 1909. 

Yellow fever patients should be isolated only in the sense of separat- 
ing them from Stegomyia calopus. This may be done by proper 
screening. It is not necessary to remove the patient to a hospital, al- 
though this is desirable, for the reason that a special hospital is more 
carefully guarded than is practicable in a private house, and the trained 
assistants are an additional safeguard. As soon as the patient is re- 
moved, the mosquitoes in the house and the surroimding houses should 
at once be destroyed. Yellow fever patients must be moved with caution, 
for the reason that undue excitement or exertion seems to increase the 
severity of the disease. 

The insecticides best suited for the destruction of mosquitoes are: 
sulphur dioxid, hydrocyanic acid gas, pyrethrum powder, tobacco smoke. 
Mini's culicide (camphor and phenol) (see page 187). At first glance 
it might appear to be a hopeless task to attempt to eradicate the yel- 
low fever mosquito in a large city, but that this is possible was demon- 


strated in Xew Orleans in 1905, when, after several months of a 
vigorous campaign, it was dilficult to find a Stegomyia mosquito. 
The measures consisted mainly in screening the water cisterns and 
eliminating all standing collections of water in and about the house- 

Historical Note. — Dr. Charles J. Finlay studied the relation of the 
mosquito to yellow fever as far hack as 1882 and 1883. The first in- 
sects used iDy the United States Army Commission to bring about the 
demonstration of the new doctrine were received from the hands of Dr. 
Finlay. Finlay believed that the cause of the disease was a micrococcus 
and considered that the insects were capable of transmitting the dis- 
ease a few days after they had stung a yellow fever patient. Stern- 
berg's studies upon yellow fever are published by the Government as 
a report of the United States Marine Hospital Service on the Etiology 
and Prevention of Yellow Fever, 1890. Carter's observations at Orville, 
Mississippi, upon the extrinsic period of incubation were published in 
the Medical Record, June 15, 1901. 

The work of the United States Army Commission appeared in the 
following publications : 

"The Etiology of Yellow Fever — a Preliminary jSTote," Proceedings 
of the 28th Annual Meeting of the Am. Pub. Health Assn., Oct. 22-26, 
1900; also Philadelphia Med. Jour., Oct. 27, 1900. 

- "The Etiology of Yellow Fever— An Additional Note," J. A. M. A., 
Feb. 16, 1901. 

"Experimental Yellow Fever," Am. Med. Jour., July 6, 1901. 

"Etiology of Yellow Fever — Supplemental Note," Am. Med. Jour., 
Feb. 22, 1902. 

On account of their historical interest and accuracy, the conclusions 
of the United States Army Commission are here given : 

1. The mosquito — C. fasciatus — serves as the intermediate host 
for the parasite of yellow fever. 

2. Yellow fever is transmitted to the non-immune individual by 
means of the bite of the mosquito that has previously fed on the blood 
of those sick with this disease. 

3. An interval of about 12 days or more after contamination ap- 
pears to be necessary before the mosquito is capable of conveying the 

4. The bite of the mosquito at an earlier period after contamina- 
tion does not appear to confer any immunity against a subsequent at- 

5. Yellow fever can also be experimentally produced by the sub- 
cutaneous injection of blood taken from the general circulation during 
the first and second days of the disease. 

6. An attack of yellow fever produced by the bite of the mosquito 


confers immunity against the subsequent injection of the blood of an 
individual suffering from the non-experimental form of this disease. 

7. The period of incubation in thirteen cases of cxj)c'rimental yel- 
low fever has varied from forty-one hours to five days and seventeen 

8. Yellow fever is not conveyed by fomites, and hence disinfection 
of articles of clothing, bedding, or merchandise, supposedly contami- 
nated by contact with those sick with this disease, is unnecessary. 

9. A house may be said to be infected with yellow fever only when 
there are present within its walls contaminated mosquitoes capable of 
conveying the parasite of this disease. 

10. The spread of the yellow fever can be most effectually con- 
trolled by measures directed to the destruction of mosquitoes and the 
protection of the sick against the bites of these insects. 

11. While the mode of proj)agation of yellow fever has now been 
definitely determined, the specific cause of this disease remains to be 

Prevention of Malaria and Yellow Fever Contrasted. — For the pre- 
vention of malaria the same principles guide us that have been set 
forth for the prevention of yellow fever. In practical application, how- 
ever, our methods of attack differ, owing to differences in the habits of 
the two mosquitoes, and owing to differences in the two diseases. The 
malarial problem is much more difficult, because it is harder to get rid 
of Anopheles than of Stegomyia. The breeding places of the yellow 
fever mosquito are practically confined to artificial containers in the 
neighborhood of human habitations, while those of anopheles are found 
in marshes, pools, or streams, and often in collections of water in the 
grass or brush. The breeding places of the malarial mosquito cover a 
much larger area, frequently the whole country, and are rather hard 
to find and difficult to destroy; also this insect travels much further 
from its breeding place than the Stegomyia, probably from three to four 
times as far. Compared to yellow fever, the control of the malarial 
human host presents special difficulties. In yellow fever man is infec- 
tive to the Stegomyia only a few days; in malaria the parasites continue 
in the circulating blood a very long time. In the case of malaria, then, 
we have to deal with chronic carriers, which, fortunately for us, does 
not occur in yellow fever. For malaria we have quinin as a prophylac- 
tic, whereas no known drug will prevent yellow fever. 


All who visit the tropics or subtropical countries where dengue pre- 
vails are very apt sooner or later to contract this infection. So far as 
known, few persons have ever died of dengue. Although the mortality 


is practically nil, the disease is a painful affection and sometimes leaves 
the body in a weakened condition for long periods of time. In its 
epidemiology and symptomatology the disease strikingly parallels yellow 
fever, which adds to its importance. Outbreaks of dengue often precede 
and may be coincident with those of yellow fever. In the tropics influ- 
enza and dengue are also frequently confused. Dengue also has some 
resemblance to the three-day fever or pappataci fever of Herzegovina, 
which is transmitted by the bite of the Phlehotomus pappatasii, a biting 


There is no definite immunity produced by an attack of dengue. 
Persons often give a history of an attack in each outbreak. The cause 
of the disease is not known. 

Graham studied dengue in Beirut, Syria, and described a protozoon 
inhabiting the red blood corpuscles and closely resembling the Plasmo- 
dium of malaria except for the absence of pigment.^ Graham believed 
that this organism underwent a developmental stage within the mos- 
quito (Culex fatigans). He claimed to have observed the spores of this 
organism "in among the cells of the salivary glands" after 48 hours in 
mosquitoes which had bitten a dengue patient upon the fourth day of 
the disease. Graham produced a very severe case of fever resembling 
dengue by inoculating a man subcutaneously with peptonized normal 
salt solution containing the salivary glands of a mosquito which had 
bitten a dengue patient 24 hours before. Graham's observations con- 
cerning the parasite in the blood and in the mosquito have not been 
confirmed, although the subject has been studied by several experienced 
microscopists. Carpenter and Sutton,- however, obtained two positive 
results out of four experimental cases of mosquito inoculation. The 
period of incubation in one of these, however, was two weeks, and the 
subjects were not sufficiently controlled to exclude the bites of other mos- 
quitoes. Agramonte ' studied an epidemic in Habana which was ac- 
companied by a plague of Culex fatigans. He attempted to transmit 
the disease by mosquitoes, trying various species at various intervals 
after the insects had fed upon dengue patients, but did not succeed in 
producing the disease in this way. Guiteras and Finlay * endeavored 
to transmit the disease with Culex pipiens, but with negative results. 
Guiteras, Finlay, Agramonte, and others who have worked upon this 
subject state that their faith remains unshaken that the mosquito acts as 
the vector of dengue, despite the negative results of their experiments. 

Ashbum and Craig ^ in 1907 studied the disease in Manila and 
showed that the virus is contained in the blood during the febrile stage. 

^Jour. Trap. Med., 1903, Vol. VI, p. 209. 

'■'Jour. A. M. A., 1905, XLIV. 

^New Yorlc Med. Jour., 1906, LXXXIV. 

*Rev. Med. Trop., 1906, Vol. VII, p. 53. 

^Philippine Jour, of Sci., Vol. II, No. 2, Section B, May 1, 1907. 


The intravenous inoculation of filtered dengue blood into healthy men 
is followed by a typical attack of the disease. The cause of the disease 
is, therefore, probably ultramicroscopic. They transmitted the infec- 
tion by the mosquito, Ciilcx fatigans, and concluded that this is probably 
the most common method of transmission. The period of incubation 
in the experimental cases averaged 3 days and 14 hours. They con- 
cluded from their studies that dengue is "not a contagious disease, and 
is infectious in the same manner as are yellow fever and malaria." 

All our preventive measures are now based upon the supposition that 
dengue is a mosquito-borne infection. At times dengue appears to be 
one of the most contagious of all diseases, for it spreads like wildfire 
and spares practically no one in the community. An instance showing 
the non-contagiousness of dengue is given by Persons, U. S. N. : A 
squad of marines from the U. S. S. Baltimore were given shore leave 
at Cavite. Twenty of the 24 marines who had been ashore came down 
with the disease after returning to the ship, while there was a total ab- 
sence of infection among those who had remained aboard. Observations 
made at the Xaval Hospital at Canacao demonstrated that in the mos- 
quito-free wards the disease did not spread, whereas when the hospital 
was located at Cavite it was noted that practically every case admitted 
became infected with dengue while under treatment for the original 
complaint (Stitt). 


The filaria is a long, slender filiform threadworm with a curved or 
spiral tail. The adult worms live in the connective tissue, lymphatics, 
and body cavities. The embryos or larva are found in great numbers 
in the blood. In several species of which the life history is known mos- 
quitoes act as the intermediate host. The most important filariae of man 
are: (1) Filaria bancroftii, the larva of which is known as Filaria 
nociurna, appearing in the blood at night and occurring especially in 
Australia and the tropics; (2) Filaria loa, the larva of which is 
known as Filaria diurna, occurring in the blood by day and prevalent in 
West Africa and India; (3) the Filaria perstans, the larva of which is 
known as Filaria perstans, which persists in the blood both day and 
night, and occurs especially in West Africa and a number of other places. 
None of these young worms do any appreciable injury in the blood; of 
the adult worms, only one. namely, Filaria hancrofti, can be viewed 
as serious, while the second species, Filaria loa, is more or less trouble- 
some. According to Manson, we are hardly justified at present in as- 
suming that all the other species are entirely without effect upon their 
hosts. These parasites infect man throughout the tropical and sub- 
tropical belt. In the United States the infection, while not very preva- 
lent, is endemic as far north as Charleston. 

FLIES 223 

According to Manson, Culex faiigans, and according to James 
the Anopheles nigerrinus, are the intermediate hosts. When fed on 
the blood of a filarial-infested individual, it is found that the filarial 
larvge soon escape from their shields in the thickened blood within the 
stomach of the mosquito. They pierce the stomach wall, enter the 
thoracic muscles of the insect, pass through a metamorphosis which 
takes from 16 to 20 daj's (longer or shorter, according to atmospheric 
temperature) ; they now quit the thorax and a few find their way to 
the abdomen; the vast majority, however, pass forward through the 
prothorax and neck, and, entering the head, coil themselves up close to 
the base of the proboscis and beneath the pharynx and under surface of 
the cephalic ganglia. This account is taken from Manson, to whose per- 
sonal interest in this disease we are indebted for the advances in our 
knowledge of the entire subject of filariasis. The wonderful prepara- 
tions of Low may be seen at the London School of Tropical Medicine, 
showing the Filana nodurna in the head and proboscis of the mosquito 
ready to come out when the proboscis of the insect pierces its victim. 
The fact that the mosquito is the intermediate host in conveying the 
infection of Filaria rests upon these observations and not upon experi- 
ments which demonstrate the actual transference of the disease. Whether 
the worm may obtain an entrance by any other channel or medium 
would, according to Manson, be hard to prove and rash to deny. Our 
correct preventive measures are based upon the theory that this is an 
insect-borne disease, although other possible modes of transference must 
not be neglected. Prophylaxis, therefore, depends upon the suppression 
of the mosquito and the prevention of the infective mosquito-bite. As 
it is not definitely known how many species of mosquitoes convey the 
infection, the preventive measures must be along general lines; a com- 
bination of those described under malaria and yellow fever, as well as 
general sanitation and personal hygiene. 


The true flies have but two wings, that is, they belong to the order 
Diptera. They comprise an enormous number of species. Not only 
have the flies a superiority in point of numbers, but entomologists are 
concluding that they probably stand at the head of the insect system 
in point of evolution; that is, they are the most highly specialized of 
all insects. Contrary to popular opinion, flies are poor scavengers. Most 
flies prefer the sunshine, but species vary greatly in their habits and 
breeding places. However, surprisingly little is known of the life his- 
tory and habits of most flies. The subject lacks attraction — especially 
the maggots or larval stage. The life history of the house fly in general 
was, down to 1873, mentioned in only three European works, and few 



Fig. 25. — House Fly {Musca domestica). 
Showing Proboscis in the Act of 
Eating Sugar. 

exact facts were given. Dr. A. S. Packard, then of Salem, Mass., 
studied the house fly and gave descriptions of all its stages, showing that 
the growth of a generation from the egg to the adult occupies from 10 
to 14 days. In 1895 Howard further traced the life history and indi- 
cated that 120 eggs are laid hy a single female, and that a generation 
is produced every 10 days at the summer temperatures of Washington. 

There may be, therefore. 12 gen- 
erations in a summer. If each 
female lays only 120 eggs (1,- 
000 have been noted), we have 
the po.ssil)ility of countless mil- 
lions coming from a single fly 
during a single season. Allow- 
ing 1,000 flies to the ounce, it 
bas been estimated that the total 
product of a single fly in 40 
days would equal 810 ])Ounds, 
provided only one-half of them 
survived ; hence, the logical time 
to begin fly suppression is in the early spring. Flies transmit disease 
in one of several ways. The biting flies, such as the tsetse flies, which 
transmit sleeping sickness, inoculate the trypanosome directly into the 
system by piercing the skin with their mouth parts. The common 
house fly does not bite. Biting flies, such as the Stomoxys calcitrans, 
abound in the United States in stables, houses, and also in nature. 
They have recently been 
implicated as go-betweens 
in poliomyelitis, and also 
in anthrax, relapsing 
fever, horse sickness 
(Pferdesterbe), and epi- 
thelioma of fowls. Other 
blood-sucking genera, 
such as Tahanus, Chry- 
sops, Hcematohia, etc., 
are of common occur- 
rence, but are not known to carry any infection regularly, although they 
might readily do so. 

The following brief account of the common house fly may be taken 
as a type of the life history and habits of flies in general. Eemedies 
and preventive measures depend upon the peculiarities in the life his- 
tory and habits of each particular genus and species. 

Life History of the Musca Domestica. — A few adults live over the 
winter in cellars, barns, attics, and out-of-the-way places, and as soon 

Fig. 26. — Eggs of House Fly as Laid in a Mass. 

FLIES 225 

as warm weather sets in they lay their eggs in manure or organic 
refuse. In 6 to 8 hours the eggs hatch into larvae (maggots), which 
grow rapidly and are fully developed in 4 or 5 days. Each larva then 

Fig. 27. — Eggs of House Fly. Some have hatched. 

becomes a pupa in a hard brown case — the puparium. In 5 days more 
the pupal case opens and the adult fly appears for a season of activity 
covering several weeks. Most of them die in the early autumn, in great 

Fig. 28. — Larv^ of House Fly. 

part due to a fungus disease, caused by Emptisa muscce, which becomes 
prevalent among the flies at this season of the year. A few are left and 
hibernate to continue the species. Hence, it takes about 10 days from 
egg to imago. It is, therefore, important to remove manure, garbage, 



Fig. 29. — Puparium of House Fly. 

and other organic refuse at least as often as this in order to prevent 
the development of the winged insects. 

The chief breeding place of common house flies is in horse manure. 
They also have been found to breed in human excrement, fermenting 

vegetable and putrefying animal 
matter, in the bedding in poultry 
pens, in refuse hog hair, in tal- 
low vats, in carcasses of varicms 
animals, and in garbage and or- 
ganic material of all kinds. All 
of which means that if we allow 
the accumulation of filth we will 
have hou>(' i]\e<. 

Life History of Stomoxys Cal_ 
citrans. — Stomoxys calcitrans, the 
biting staljle tly, is very similar 
to the house fly in its life history 
and in appearance during the 
preparatory stages, but develops 
more slowly, requiring nearly a 
month to undergo a complete life 
cvde. The eggs are laid like those of the house fly in horse "manure, 
but more frequently in fermenting heaps of grass, cow-dung, brewers 
refuse ("spent hops"), etc. The adult flies are much like the house 
fly, but have a sharp, needle-like proboscis. They feed exclusively on. 
mammalian blood and are 
a great annoyance to 
horses and cattle in late 
summer and autumn. 
They bite persons less 
frequently, but are of im- 
portance on account of 
their relation to polio- 
myelitis, anthrax, etc. 
The stable fly can best be 
controlled by eliminating 
its breeding places. 

Flies as Mechanical 
Carriers of Infection. — 
Leidy in 18G4 attributed 

the spread of gangrene in hospitals during the Civil ^Ya^ to the agency 
of the house fly. Shortly thereafter it was discovered that the bite of 
the gad-fly may transmit anthrax from cattle to man. Later it was 
found that purulent ophthalmia of the Egyptians is carried by the house 

Fig. 30. — Stable Fly (^Stomoxys calcitrans). (Brues. 



Fig. 31. — Head show- 
ing Proboscis, 
Stomoxys Calci- 
TKANS. (Brues.) 

fly, and the spread of an infectious conjunctivitis known as "pink eye" 
in the South has heen shown by Hubbard to be facilitated by little 
midges of the genus Hippelates. Eeference has already been made to 
the bite of the tsetse flies in spreading nagana, sleeping sickness, and 
other trypanosomatic infections. Eeeently the stable fly has been shown 
to be able to transmit various infections in a mechanical way. 

It is now known that typhoid fever and other intestinal infections 
may be transmitted by the common house fly. Celli 
in 1888 fed flies with pure cultures of typhoid, 
and showed that the virulent bacilli were passed 
in the dejecta. Kober in 1895 was one of the first 
to call special attention to the danger of contami- 
nating food supplies by flies coming from the ex- 
creta of typhoid patients. The United States 
Army Commission — Keed, Vaughan, and Shake- 
speare — studied the presence of typhoid fever in 
our camps during the Spanish- American war in the 
summer of 1898. They concluded that flies un- 
doubtedly serve as carriers of the infection. '"Flies 
swarm over infected fecal matter in the pits and then deposit it and 
feed upon the food prepared for the soldiers at the mess tents. In some 
instances, where lime had recently been sprinkled over the contents of 
the pits, flies with their feet whitened with lime were seen walking over 
the food." Vaughan subsequently stated that he considered that about 
15 per cent, of the cases of typhoid in the camps were caused by fly 


Alice Hamilton ^ iso- 
lated typhoid bacilli from 
5 out of 18 house flies 
captured in Chicago in 
the privies and fence 
near a sick room. It has 
been shown experi- 
mentally that living, ty- 
phoid bacilli may re- 
main in or upon the 
bodies of flies for as long as 23 days after infection. 

Howard studied fly abundance in relation to the origin and preva- 
lence of typhoid fever in the District of Columbia in the summer of 
1908.^ No particular correlation between the prevalence of the flies and 
the prevalence of the disease could be made out. 



_,. — ' 

— -"^..^ 




— ""^ 








Fig. 32. — Wing of Stable Fly (Stomoxys calcitrans). 

^Jour. A. M. A., 1903, 40, p. 576. 

^Rosenau, Lumsden, and Kastle: Report No. 3, 1908, P. H. and M. H. S., 
Hygienic Laboratory Bull. No. 52. 



Flies undoubtedly spread the infection of typhoid fever, hut the im- 
portance of the role they jjlay in this regard varies considerably with 
circumstances. In camps, unsewered towns, and overcrowded places in 
poor sanitary condition the danger from flies may ho considerable, but 
even under the worst conditions it is doul)tful whether flies ever play 
the major role or are responsible for the bulk of typhoid fever, as has 
leen stated. In a well-sewered city, such as Washington, we concluded 
that the flies are probably responsible but for an occasional case of the 
disease. It is very difficult in any particular instance to know quantita- 
tively just how much of the infection is conveyed by flies and how 
much by contacts. The danger of flies is great enough without the need 
of exaggeration, and their suppression fully justifies the best energies 
of the health officer. It is perhaps a mistake to call the common house 
fly the "ty})hoid fly," not alone for the reason that tlie disease is spread 
in many other ways, but for the reason that the fly is responsible for 

the spread of many infec- 
tions other than typhoid 
fever. Flies undoubtedly 
play the same role in 
dysentery, cholera, and 
all other intestinal infec- 
tions that they do in 
typlioid fever. Tizzoni 
and Cattani in 1896 dem- 
onstrated active cholera 
organisms in the dejecta 
of flies caught in the 
cholera colonies of 
Bologna, Italy. These 
observations were subsequently verified and extended by Simonds, Offel- 
man, McEae, and others. 

It is now quite evident that flies lighting upon a case of smallpox, 
measles, scarlet fever, and other exanthematous disease may very readily 
transmit these infections to another person. I have actually seen mag- 
gots breeding in the open lesions of a case of smallpox treated in the 
open air at Eagle Pass, Texas. 

Flies may, in the same mechanical wa}^ transmit the infection of 
erysipelas, anthrax, glanders, and other skin infections. It is known 
that flies may ingest tuberculous sputum and excrete tubercle bacilli 
which may remain virulent as long as 15 days. Flies have also been 
associated with leprosy and many other diseases. 

Esten and Mason ^ counted the bacterial population of 415 flies and 
found that the number of bacteria on a single fly may range all the 
^Store's Agricultural Experiment Station, Bull. No. 51, April, 1908. 

Fig. 33. — The "Little House Fly" (Homulomyia 
canicularis i ). (Hewitt.) 



way from 550 to 6,600^000. Early in the fly season the numbers of 
bacteria on flies are comparatively small, while later the numbers are 
comparatively very large. The places where flies live also determine 
largely the number of bacteria they carry. The average of the 415 flies 
was about one and one-quarter million bacteria. The method of the ex- 
periment was to introduce the flies into a sterile bottle and pour into the 
bottle a known quantity of sterilized water, then shake the bottle to 
wash the bacteria from the body of the fly. The numbers, therefore, 
only represent those carried on the outside and not those in the intestinal 
tract. The experiments of Esten and Mason were designed to simulate 
the number of microorganisms that would come from a fly in falling 
into milk. 

Torrey ^ found that a single fly may carry from 570 to 4,400,000 
bacteria upon its surface, and from 16,000 to 38,000,000 in its intes- 
tinal-tract. The prevailing types are Streptococctis equiniis fecalis and 

Fig. 34. — Wing op House Fly, Showing How It Carries Dust Particles. 

salivarius, which are also found in the breeding and feeding places of 
the house fly. Torrey also obtained three cultures of B. paratypliosus, 
which is especially significant. 

Even though flies breed in manure, and the larvae teem with bacteria, 
the adult winged insect, when newly hatched, contains fewer micro- 
organisms. This cleansing is due to the active phagocytosis which takes 
place during metamorphosis from pupa to imago. The bacteria in the 
intestinal tract of the newly hatched imago are mostly extruded soon 
after emergence from the puparium. 

Bacot,^ however, has shown that certain species of bacilli ingested 
during the larval period of Musca domestica can retain their existence 
while their host is undergoing the process of metamorphosis, and con- 
tinue their existence in the gut of the adult fly, but that their number 
diminishes suddenly after emergence. In a subsequent work Bacot^ 

^J. A. M. A., May 11, 1912, LVIII, No. 19, p. 1445. 
' Trans. Ento. Soc, London, 1911, Part II, p. 497. 
"" Parasitology, IV, I, Mar., 1911, p. 68. 


demonstrated that Bacillus pyocyaneus may thus survive. Faichnie * 
shows how B. typhosus may also persist. Ledingliam confirms tlu'se con- 
clusions, and states that he has recently isolated B. typhosus from pupa, 
the larva> of which have fed on tliis organism. 

Graham-Smith - recovered B. anthracis from blow flies bred from 
larvae fed on meat infected with tlie organism, but failed to recover 
B. typhosus and B. entpritidis. 

Among the list of diseases of wiiich there is more or less evidence 
that the infection may be conveyed by files are: typhoid, cholera, dysen- 
tery, diarrhea in infants, anthrax, yaws, erysipelas, ophthalmia, diph- 
theria, smallpox, plague, tropical sore, parasitic worms, sleeping sick- 
ness, poliomyelitis, relapsing fever, and several infections of the lower 

An interesting light was thrown on the possible modes of dissemina- 
tion of the eggs and larvae of hookworms by Galli-Valerio (1905). He 
phiced eggs and larva? of Ankylostouia duodenaUs in a bottle with flies, 
and on washing found many eggs and encapsulated larvae which had 
adhered to their bodies, but none in the flies' intestines. 

Flies may transmit the virus of disease mechanically, either through 
their dejecta or upon their mouth parts, legs, and other surfaces of the 
body. The flies may carry the infection directly to our lips or indirectly 
to our fond or to any surface upon which they light. 

Suppression. — The suppression of the common house fly may be ac- 
complished by striking at their breeding places. In a city this does not 
present very great difficulty. It resolves itself simply into a matter of 
cleanliness — organic cleanliness of our environment. The chief breed- 
ing places are in horse manure and garbage. These should be given 
first attention. One neglected stable will furnish a plague of flies for 
an entire neighborhood. Their suppression in a well ordered city for- 
tunately is neither expensive nor difficult, but it requires a well-trained 
and capable corps of inspectors with sufficient autliority to enforce the 
regulations. The suppression of flies by voluntary effort through the 
slow process of education cannot be relied upon. 

In cities stable manure should be placed in properly covered recep- 
tacles and removed at least once a week. Tliis one measure obviates the 
use of kerosene, chlorid of lime. Paris green, or arsenate of lead, all of 
which are expensive and uncertain unless used frequently and in lib- 
eral amounts ; further, they decrease the fertilizing value of the manure. 

Garbage should be kept in water-tight cans with good covers and 
removed frequently, especially in the warm weather. Eefuse on city 
lots, in back yards, in alleys, about wharves, markets, and similar places 
where organic matter collects should be regularly and faithfully taken 

^ Jour. Boy. Army Med. Corps, XIII, 1909. 

^'Eepts. to Local Gov. Bd., New Series, No. 53, 1911. 



Fig. 35.— The Hodge Fly Thap 
ON A Garbage Can. 

away. Householders, provision merchants, storekeepers, and others 
should be held responsible for the cleanliness and tidiness of their prem- 
ises, and those who violate these 
simple and primitive hygienic re- 
quirements should have their places 
cleaned up for them at their own 
expense. The orders of the Health 
Department of the District of Co- 
lumbia, published May 3, 1906, are 
excellent, and, if carried out, would 
be very effective. These orders may 
be briefly condensed as follows : 

All stalls in which animals are 
kept shall have the surface of the 
ground covered with a water-tight 
floor. Every person occupying a 
building where domestic animals are 
kept shall maintain, in connection 
therewith, a bin or pit for the recep- 
tion of manure, and, pending the 
removal from the premises of the 
manure from the animal or animals, shall place such manure in said 
bin or pit. This bin shall be so constructed as to exclude rain water, 
and shall in all other respects be water-tight, except as it may be con- 
nected with the public sewer. It shall be provided with a suitable cover 
and constructed so as to prevent the ingress and egress of flies. No 
person owning a stable shall keep any manure or permit any manure 
to be kept in or upon any portion of the premises other than the bin 
or pit described, nor shall he allow any such bin or pit to be overfilled 
or needlessly uncovered. Horse manure may be kept tightly rammed 
into well-covered barrels for the purpose of removal in such barrels. 
Every person keeping manure in any of the more densely populated 
parts of the District shall cause all such manure to be removed from 
the premises at least twice every week between June 1 and October 31, 
and at least once every week between Kovember 1 and May 31. No 
person shall remove or transport any manure over any public highway 
in any of the more densely populated parts of the District except in a 
tight vehicle, which, if not closed, must be effectually covered with 
canvas, so as to prevent the manure from being dropped. No person 
shall deposit manure removed from the bins or pits within any of the 
more densely populated parts of the District without a permit from 
the health officer. Any person violating any of these provisions shall, 
upon conviction thereof, be punished by a fine of not more than $40 
for each offense. 


In addition to this ordinance, others have been issued by the 
health department of the District of Columbia which provide against 
the contamination of exposed food by flies and by dust. The ordinances 
are excellently worded so as to cover all possible cases. They provide 
for the registration of all stores, markets, cafes, lunch rooms, or any 
other places where food or beverage is manufactured, prepared, stored, 
offered for sale, or sold. 

Where it is not practicable to remove manure, it may be kept cov- 
ered in a dark place, which discourages the visitation and breeding of 
flies, and in addition should be carefully screened. Flies may be de- 
stroyed with sulphur dioxid, carbon bisulphid, hydrocyanic acid gas, 
petroleum, chlorinated lime, Paris green, and other insecticides. Kero- 
sene (petroleum) poured upon manure, garbage, and other fly-breeding 
places is effective ; it kills the larvae. Lime is not effective ; chlorinated 
lime is good, but is not practical, for, like all other substances used 
for this purpose, it needs frequent application and in generous amounts. 

Flies are thirsty insects and will be attracted to a saucer of water 
containing a little formalin (4 per cent.). This simple measure will 
kill many of them in a room. The salts of barium, cobalt, and other 
poisons, such as arsenic, potassium bichromate, or quassia infusion, may 
be used instead of formalin, and are better bait if sweetened. Sticky 
fly-paper, fly traps, electric fans, and other well-known measures will 
help dispose of a certain number of flies, but all these measures are 
tentative, and attack the problem at the wrong end. 

The fly has a number of natural enemies: various fungi, especially 
one belonging to the Entomoplitliorece, which destroys flies in the autumn. 
Flies also harbor protozoa and nematodes as parasites, which, however, 
seem to do them little harm. The little bright red objects often 
seen attached to flies are mites, which are usually only temporary ecto- 
parasites stealing a free ride. When spider webs are not disturbed they 
catch, and the spiders devour, a large number of flies. The house centi- 
pede (Scutigera) also sometimes catches and eats flies, as do the com- 
mon garden toad, some lizards, and a few insectivorous birds. 

Flies and similar dipterous insects are responsible for the trans- 
mission of a large number of diseases, most of which are discussed else- 
where. It now remains to consider sleeping sickness, transmitted by 
the tsetse fly {Glossina palpalis), and pappataci fever, transmitted by 
a biting dipterous insect (Phlehotomus pappatasii). For convenience 
a general consideration of the trypanosomes is inserted in this chapter. 


Sleeping sickness was limited to tropical Africa, especially in the 
Congo, on the shores of Victoria Nyanza, and about the head waters 



of the ISTile, 'but is gradually spreading. Many thousands have perished 
from this infection, caused by Trypanosoma gamMense and transmit- 
ted by the tsetse fly (Glossina palpalis). The disease is characterized 
by two stages: in the first there are irregular fever, glandular enlarge- 
ments, an erythematous rash, and localized edemas. In the second 
there are slowly increasing lethargy and other morbid, nervous symp- 
toms. After a chronic course sleeping sickness usually terminates in 
death; few cases recover. Many instances of fatal homesickness in the 
negroes during the slave trade are now believed to have been this 

The Trypanosoma gamhiense was discovered by Button in 1901 dur- 
ing the first or febrile stage of sleeping sickness, and subsequently 
studied by Button and Todd, who did not at first suspect the relation 
of the trypanosome to sleeping sickness. This was shown by Castellane 
in 1903. The trypanosomes are found in the cerebrospinal fluid, in 
the enlarged lymphatic glands, and also in the circulating blood. It 
seems that when the trypanosomes are inoculated through the skin by 
the tsetse fly they are temporarily blocked by the lymphatic glands. 
From here small numbers of them pass into the circulation and thus 
to other parts of the body. They are always in the fluids; never in the 
cells or tissues. Novy and McNeal in 1903 accomplished the remarkable 
feat of growing trypanosomes in the water of condensation of blood 
agar tubes. Pure cultures show marked differences between the Trypano- 
soma lewisi of the rat and the Trypanosoma grussei of horses and other 
domestic animals. So far no one has succeeded in cultivating the Try- 
panosoma gamhiense in 
artiflcial culture media. 

The relation of the 
tsetse fly to the transmis- 
sion of this disease rests 
upon satisfactory evi- 
dence. Button and 
Todd, as well as others, 
find these fiies abundant 
wherever sleeping sick- 
ness exists. Wherever 
the Glossina palpalis is 
absent sleeping sickness 
never spreads, as Koch 
observed; while, on the 
other hand, if a case is brought to a locality where the tsetse fly pre- 
vails, it soon spreads. It is probable that the transmission by the tsetse 
fly is not of the simple mechanical type, but that the parasite undergoes 
a sexual evolution within the insect. Flies seena to lose their power of 

Fig. 36. — Tsetse Fly (Glossina palpalis). 


transmission soon after feeding on an infected animal, and Bruce con- 
siders it thoroughly im])ossible tluit mechanical transuiission alone could 
e.\])lain the situation. Kleine's cxjx'riiiicnt on monkeys, confirmed by 
Bruce, siiowed that tlie Hies may convey the disease '^1 days after one 
feeding upon a monkey infected with sleeping sickness. In another 
experiment by Taute, which is i-epoi'ted l)y Kleine, infection was })ro- 
duced on each of the first three days after feeding. From the fourth 
to the tenth day no infection resulted. The flies then became infective 
again and pr()(Uu'ed the disease from the eleventh to t]:e forty-fourth 
day. Kleine ' concludes that the period of development or intrinsic 
period of incubation in the fly is about 20 days or a little loss. Flies 
remain infective at least 75 days. Not all flies which drink lihiod con- 
taining trypanosomes become infective. The proportion is about 1 in 
20. Of the flies caught in nature in endemic areas, from 2 to 10 in one 
tliousand are capable of transmitting the disease to animals. Novy has 
emphasized, and Minchini has corroborated the fact, that tsetse flies 
may harbor non-pathogenic as well as pathogenic trypanosomes, a fact 
which impairs the value of a great deal of the microscopic work which 
has been done. As a means of avoiding the accident of dealing with 
naturally infected flies, it is best to use those which have been bred 
and raised in the laboratory. 

Prevention. — The prevention of sleeping sickness in the present state 
of our knowledge depends first upon isolation of the sick, protecting 
both the sick and the well against fly bites, and the suppression of the 
flies themselves. The sick should be isolated in a location where GIos- 
sina paJpalis is absent, or in a w^ell-screened and carefully managed 
hospital. It is especially important to isolate all those who carry the 
infection in the early stages of the disease, whether they feel sick or 
not. It is not sufficient simply to isolate those who have enlarged 
glands, but careful blood examinations must be made. The trypano- 
somes have been found in the circulating blood of persons with normal 
lymph glands. 

All persons taken to the hospital and detention station are given a 
thorough treatment with atoxyl (a combination of arscnious acid and 
anilin oil). Atoxyl is one-tenth as toxic and contains about three times 
as much arsenic as arsenious acid alone. The dose is from % to 3 
grains (0.05-0.2 grams) subcutaneously. 

The extermination of the tsetse fly seems a hopeless task. The 
larvae remain in the body of the mother fly until fully developed and 
are then dropped on jnoist soil, in which they burrow to undergo trans- 
formation to the adult state; therefore, clearing of the land in limited 
locations largely diminishes the number of flies. Clearing the brush 
exposes the earth to the sun, and the surface becomes dry and hard, so 

^ Bull, of the Sleeping Sickness Bureau, No. 7, 1909, 



that flies die during the pupal period. This measure has limited possi- 
bilitieSj but is useful, as Shirata points out, around ports^ in the neigh- 
borhood of villages, wharves, and other places. 

The tsetse fly may also be fought by suppressing its food supply. It 
must obtain the blood of some vertebrate animal every two or three days. 

1. Culicoides milnei, Austen. 

3. Culicoides grahamii, Austen. 

5. Simulium latipes, Mg. 

7. Simulium wellmanni, Rouband. 

•Various Gnats 

2. Culicoides brucei, Austen. 

4. Phlebotomus duboscqi, Neven -Lem.aire 

6. Simulium damnosum, Theob. 

8. Simulium griseicollis, Becker. 

Simulium is implicated in pellagra; Phlebotomus in pappataci fever. 

The German Commission has shown that on the banks of the Victoria 
Nyanza the tsetse fly lives largely upon crocodile blood. This fact was 
discovered by the interesting observation that the flies frequently con- 
tain parasites peculiar to the crocodile's blood. Koch believes that the 
disease may be successfully controlled by destruction of the crocodiles, 
a theory which later research has rendered, very unlikely. 


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FLEAS 237 

Todd and Wolbach ^ suggest a systematic examination of the natives 
in the endemic area by gland palpation and gland puncture. The lat- 
ter consists in withdrawing a drop of fluid from one of the enlarged 
lymphatic glands by means of a hypodermic syringe. The little drop 
of bloody fluid thus obtained is examined as a fresh preparation under 
the microscope for trypanosomes. By this method these investigators 
found at least 0.8 per cent, of the population of the Gambia to harbor 
trypanosomes. If all the infected individiials could be collected in vil- 
lages for observation^ treatment, and isolation, it would do much to 
limit the disease. 

Trypanosomes are the cause of numerous other diseases in animals, 
as will be seen by reference to the table on page 236. So far as known, 
sleeping sickness is the only important disease of man produced by 
trypanosomes. Kala-azar, however, is produced by a flagellated proto- 
zoon parasite which probably belongs to the trypanosomes. 

Practically all animals are susceptible to almost all trypanosomes. 
The trypanosomes which infect man may readily be transmitted to mon- 
keys, guinea-pigs, rabbits, etc. 


Doerr and Euss - and also Doerr, Franz, and Taussig originally de- 
scribed a three-day fever which occurs on the shores of the Adriatic, 
the cause of which is not known, but which is of special interest for 
the reason that it has been demonstrated to be transmitted through the 
bite of a dipterous insect commonly called a gnat — Phlehotomus pap- 


Fleas are flat, wingless insects related to the Diptera. They pass 
through a complete metamorphosis : embryo, larva, pupa, and imago. 
The adult female flea deposits her eggs among the hair or fur of the 
host animal, but, unlike the eggs of many ectoparasites, they are not 
fastened to the hairs and therefore fall freely to the ground. The eggs 
are oval, whitish, and smooth and about half a millimeter long. The 
larvas escape from the eggs in 2 to 5 days. They are able to break the 
egg shell by a slender process on the top of the head which disappears 
after the first molt. The larva is a slender, legless, cylindrical creature, 
whitish or yellowish in color, with a head and 13 segments. There are a 
few scattered hairs or bristles on the body, and at the tip is a pair of cor- 
neus processes. At the front of the head is a pair of biting jaws or 

^Annals of Tropical Medicine and Parasitology, Vol. V, No. 2, Aug., 1911, 
p. 245. 

^ ScMffs und Tropen Myg., 1909, Vot XIII, No. 22, p. 693. 



mandibles. The lan'ae feed on almost any kind of refuse. They have 
been reared on the sweepings from rooms. There is always some or- 
ganic matter in such dust, and this is doubtless their nourishment. In 
houses the larvae usually crawl into cracks or in carpets, where they feed 

FiQ. 38. — The Indian Rat Flea (Lcemopsylla cheopis Rothsc). 

and grow. Those that infest wild animals probably feed on the refuse 
in the nests or retreats of these animals. It will be noticed that, con- 
trary to the mosquito, the larval and pupal stages of the flea are not 
aquatic. They remain in the larval stage from a week to ten days, 
sometimes two weeks, molting the skin three times in this interval. 
Then they spin flat, white, silken cocoons in which they transform to 
the pupal stage. In from 5 to 8 days the adult flea emerges from the 
cocoon. The period of their transformation is affected by the tempera- 
ture and moisture. In warm, damp weather a generation may develop 
in ten da3's or two weeks, but usually about 18 days to three weeks 
elapse from the egg to the adult. Although some moisture is neces- 
sary for their development, an excess is apt to destroy the larva?. 

The leaping ability of adult fleas is familiar to all. This, however, 
has been greatly exaggerated. The British Plague Commission de- 
termined that fleas jump 3 to 5 inches, never over 6. jSTo part of the 
leg is particularly enlarged, so that tlie jump is made by the entire 
leg, as in the leaf-hopper insect, and not by the femur of the hind leg, 
as in the grass-hopper. Fleas do not vary much in size. They are 
mostly about 2 to 3 millimeters long. The adult insect has a hard, 
strongly chitinized body. The mouth parts resemble somewhat those 
of the mosquito. Both the male and the female flea are capable of 
piercing the skin to obtain blood and thus transmit infection. Fleas, 
as a rule, prefer certain hosts, but are not as particular in this regard 
as are many parasites. Those species which are best known are found 
to attack several hosts, including man. This is one reason that makes 



them dangerous parasites, so far as plague and other infections are 
concerned. Over 300 species are described. Formerly all fleas were 
classified in the single family PulicidEe, genus PuJex; now they are ar- 
ranged in many genera and these genera grouped into families.^ 




^^K .■ ^rr^if ^ 


BPlMfc.' jtowMK "^x »^- 

Vv ? 



Fig. 39. — The Common Rat Flea of Europe and Noeth Amebica (Ceratophylliis 

fasciatus Bosc). 

Pulex serraticeps or Ctenocephalm cants occurs all over the world, 
infesting cats and dogs, also many other animals. They are fre- 
quently brought into houses upon domestic animals, and thus become 
troublesome to man. Pulex irritans is the human flea, sometimes called 
the "house flea" or "common flea." 

Fig. 40. — The Human Flea (Pulex irritans Linn.). 

The fleas concerned in the transmission of plague are Loemopsylla 
cheopis, the Indian rat flea, and CeratopJiyllus fasciatus, the common 
rat flea of Europe and North America. Plague may also be transmitted 
by Ctenocephalus felis, the cat flea; Pulex irritans, the human flea; 
Ceratophylhis acutus, the squirrel flea, and doubtless other genera and 

* Banks: "The Rat and Its Relation to the Public Health," P. H. and M. 
H. S., p. 69, 


In addition fleas act as intermediate hosts for certain tapeworms 
{Dipylidium coninum), and doubtless are the mechanical or biological 
carriers of other infections. Xicolle incriminates the flea in typhus 

Pulicides. — Adult fleas succumb to the agents applicable to in- 
sects in general. Mitzmain ^ has shown that water is of little value in 
the destruction of mature fleas. Glycerin is also practically inert as a 
pulicide, but tincture of green soap is very quick and effective. This 
action cannot be due to the alcohol in the soap, for alcohol in the 
strength of 70 per cent, and absolute is uncertain in its action and 
practically inefficient. Kerosene (coal oil) is a very efficient flea de- 
stroyer. Formalin, phenol, mercuric bichlorid, and tricresol in the 
strength used as disinfectants are of little value in killing fleas. Pow- 
dered sulphur seems to be of no value. 

Of gases, bisulphid of carbon (CSj), hydrocyanic acid gas (HCN), 
and sulphur dioxid (SO,) are highly efficient in the strengths recom- 
mended for general insecticidal purposes. Chloroform or ether first 
anesthetizes fleas, and if continued kills them. This is important for 
the safe handling of rats, squirrels, and other plague animals. The 
host may be chloroformed and the fleas and other ectoparasites re- 
moved with a comb. The anesthetic may be controlled by practice so 
that the host will recover and the fleas die, or both recover, or both die, 
as may be desired. 

In flea-infected houses the larvge. living in the cracks of the floor, 
etc., may be easily controlled by sprinkling a thin coating of flake naph- 
thalene on the floor and then leaving the room tightly closed over night. 
In the morning the naphthalene may be swept up and what remains 
used again. 


Plague is primarily a disease of the rat and secondarily of man. 
This fact is now firmly established not only by the recent experiences, 
but especially through the admirable studies of the Indian Plague Com- 
mission,- which established beyond doubt the fact that plague may be 
and generally is transmitted from rat to rat and from rat to man 
through the agency of the flea — Locmopsylla cheopis — and sometimes by 
CeratopJiyllus fasciatus, et al. During some plague epidemics it has been 
noted that the rats die in great numbers before and during the out- 
break. It is now known that this epizootic in the rat is true plague. 
In nature, rats suffer both with acute and chronic plague. 

In the laborator}', rats may be infected with plague by ingestion, by 

' Public Health Beports, July 29. 1910, Vol. XXV. No. 30, p. 1039. 

'Journal of Hygiene, Vol. VI, No. 4; Vol. VII, Nos. 3, 6; Vol. VIII, No. 2. 


application of the virus to rtmcous or cutaneous surfaces, or by sub- 
cutaneous inoculation. In nature, rats may become infected by any of 
these means or through flea bites. 

Eats are great travelers, and have carried the plague to all quarters 
of the globe. A more complete discussion of the rat and its relation 
to plague and other diseases will be found on page 242. 

Within the past few years it has been discovered that, while the 
rat is the great medium for the spread of plague, the disease is probably 
preserved from extinction in Thibet by another rodent, the marmot 
(Arctomys hohac). In California the infection has gotten into the 
ground squirrels (Citellus heecheyi), in which the disease will doubt- 
less be kept alive for many years to come. To realize the full impor- 
tance of these discoveries, it is only necessary to call to mind that, in 
order to eradicate plague forever from the surface of the globe, a war- 

FiG. 41. — A SQuraREL Flea (Hoplopsyllus anomalus Baker.). 

fare against the rat alone is not sufficient, but must include the ro- 
dents mentioned and perhaps others. 

Simond in 1897 advanced the theory that plague was carried by 
fleas. This theory was developed by J. Ashburton Thompson and others 
and conclusively proved by the Indian Plague Commission. The exact 
method by which the flea transmits the infection from animal to ani- 
mal is not definitely understood. The mouth parts appear not to re- 
main infected. It is possible that the salivary secretions contain the 
microorganisms. It is known that the plague bacilli may live in the 
digestive tract and be passed in live and virulent numbers in the de- 
jecta. It is easy to understand how some of the infected dejecta may 
be rubbed or scratched into the little wound produced by the flea bite. 
Wlien it was found that the common rat flea of Europe, the Cej-atophyl- 
lus fasciatus, does not readily bite man, considerable doubt Avas thrown 
upon the part played by the flea in plague transmission. These nega- 
tive results, however, are offset by the convincing positive proofs of the 
British Plague Commission in India, and by McCoy and Mitzmain in 


San Francisco, who showed tliat under certain conditions the rat flea 
will bite man, es])eciallj if the natural food siipi)ly is limited, and that 
these fleas may feed on a man's hand even in the presence of a rat. 

Eaybaud ^ calls attention to the fact that the rat flea {Ceratophyllus 
fasciatus) is able to hibernate for a month or 45 days without nourish- 
ment, and that virulent plague germs may persist unharmed in its 
stomach during this length of time and even longer. This fact may 
be of importance for the transmission of plague to a distance. 

It should be remembered that, according to the observations of Nut- 
tall and Yersin, flies and possibly other insects may also occasionally 
convey the infection. Walker - considers, as the result of experiments, 
that bedbugs and other biting insects play an important role in the 
transmission of plague. 


Eats, mice, squirrels, and other rodents have become a serious prob- 
lem in preventive medicine, and their habits and methods of suppression 
may be considered conveniently at this place. Plague being primarily 
a disease of rats, the prevention and suppression of this infection re- 
solve themselves into a war upon these rodents. For the control of plague 
it is, therefore, necessary to have a knowledge of the life history and 
mctliods of attacking the problem in the lower animals. In addition to 
plague, rats are the great reservoir of trichinosis. They are responsible 
for the transmission of certain tapeworms and other parasites. They 
arc subject to leprosy, cancer, and numerous other diseases, some of 
which concern man. 

Rodents comprise more than one-third of all living species of mam- 
mals, and exceed any other mammalian order in the number of in- 
dividuals. They have no canine teeth, but strongly developed incisors. 
Only the front of the incisors is covered with enamel, which keeps 
them sharp and chisel-like, owing to the more rapid wearing away of 
the softer dentine. The incisor teeth continue to grow throughout the 
life of the animal. The most extensive family of rodents is the Muridce, 
which includes the true rats and mice, typified by the genus Mils. 
Trouessart, in his "Catalogus mammalium," enumerates 250 species of 
Mws described before 1905. Since that date a number of new forms 
have been described. 

The genus Mus is characterized by narrow, ungrooved incisors ; three 
small-rooted molars; soft fur mixed with hairs, sometimes with spines; 
a rudimentary pollex (thumb) having a short nail instead of a claw; 
a long tail bearing rings or overlapping scales and often naked or 

^Presse Medicale, March 8, 1911, No. 20. 
'Walker: Indian Med. Gas.. 1910, No. 3. p. 93. 


nearly so. The ears are rather large, the eyes bright and prominent, 
and the muzzle somewhat pointed. 

The distinction between rats and mice is arbitrary and based on 
size. Of the many species of the genus Mus only three or four have 
developed the ability to adapt themselves to such a variety of condi- 
tions as to become cosmopolitan. Four have found lodgment in Amer- 
ica : . 

The common house mouse, Mus musculus. 
The English black rat, Mus rattus. 
The Egyptian or roof rat, Mus alexandrinus. 
The brown rat, TIfws norvegicus. 

The black rat and the roof rat differ from each other mostly in 
color, and some zoologists' regard them as races of the same species. 
The brown rat is also known as the gray rat, barn rat, wharf rat, sewer 
rat, and Norway rat. 

The black rat {Mus rattus) has been known in Europe since the 
twelfth century, and from there has been carried to America. The. 
brown rat (Mu^ norvegicus) came later, and, as it is more destructive, 
larger, and more ferocious, it is rapidly driving the black rat before it. 
The brown rat differs somewhat in habits from the black rat, especially 
in that it burrows, which protects it against its enemies and renders its 
suppression more difficult. 

The house mouse holds its own everywhere against the brown or 
Norway rat, as it is able to get into holes too small for the rat to fol- 
low. Albinism and melinism occur in all species; pied forms are com- 
mon. The white rat of the laboratory is an albino form of either Mv^ 
rattus or Mus norvegicus. 

Breeding" and Prevalence. — The brown rat is more prolific than 
either the roof rat or the black rat. The brown rat reproduces from 
three to five times a year, each time bringing forth from six to nine, 
and sometimes as many as 22 or 23, young. They breed more rapidly 
in temperate and equable climates than in those of great variability. 
The number of rats is only limited by the food supply and opportu- 
nities to nest. Few people have any conception of the enormous num- 
bers of rats in cities and on farms. Although few are seen in the day 
time, at night they fairly swarm along river fronts and wharves, as 
well as in sewers, stables, warehouses, markets, and other places where 
food may be found. A few instances will illustrate the prolific habits 
and give an idea of the destructive tendency of rats. 

In 1901 an estate near Chichester, England, was badly infested with 
rats;^ 31,981 were killed by traps, poisons, and ferrets, while it is esti- 

^ The Field, London, Vol. C, p. 545, 1902. 


mated that tenants, at the threshing, destroyed fully 5,000 more. Even 
then the property was by no means free from rats. 

During the phigue of rats on the island of Jamaica, in 1833. the 
number killed on a single plantation in a year was 38,000.^ The in- 
jury to sugar cane on the island caused by the animals was at that time 
estimated at half a million dollars a year. 

The report of the Indian Famine Commission in 1881 affords one 
of the best illustrations of the number of rats that may infest a coun- 
try. An extraordinary number of the animals at tliat time inhabited 
the Southern Deccan and Mahratta districts of India.- The autumn 
crop of 1878 and the spring crop of 1879 were both below the average, 
and a large portion of each was destroyed by rats. The resulting 
scarcity of food led to the payment of rewards for the destruction of 
the pests, and over 12,000,000 were killed. 

Migration. — The migrations of rats have often been recorded. The 
brown rat is known in Europe quite generally as the migratory rat; 
the Germans call it the Wanderrattc. Pallas relates that in the autumn 
of 1772 they arrived from the East at Astrakhan, southeastern Russia, 
in such great numbers and so suddenly that nothing could be done to 
oppose them. They crossed the Volga in immense troops. The cause 
of this general migration was attributed to an earthquake, but, since 
similar movements of the same species often occur without earthquakes, 
it is probable that only the food supply of the animals was involved 
in the migration which first brought the brown rat to Europe. 

Seasonal movements of rats from houses and barns to the open 
fields take place in the spring, when green and succulent plant food is 
ready for them. The return movement takes place in the autumn. 
This seasonal migration is nota])le even in large cities. In 1903 a 
multitude of migrating rats spread over several counties of western 
Illinois. They traveled in great armies and invaded the farms and 
villages of Rock Island and Mercer counties, and caused heavy losses 
during the winter and summer of 1904. In one month Mr. Montgom- 
ery of Mercer county killed 3,435 rats on his farm. He caught most of 
them in traps. 

In England a general movement of rats inland from the coast oc- 
curs every October. This is known to be closely connected with the 
closing of the herring season. During the fishing the rodents swarm 
to the coast attracted by the offal left in cleaning the herring, and 
when this food fails the animals troop back to the farms and villages. 

An invasion of rats (Mus rattus) in the Bermuda Islands occurred 
about the year 1615. Within two years they had increased so alarmingly 
that none of the islands was free from them. The rodents "devoured 

^New England Farmer, Vol. XII, p. 315, 1834. 
^British Med. Jour., Sept. 16, 1905, p. 623. 


everytliing that came in their way — fruits, plants, and even trees" — so 
that for a year or two the people were nearly destitute of food. A law 
was passed requiring every man in the island to keep 12 traps. In 
spite of all efforts the animals continued to increase imtil they finally 
disappeared, so suddenly that it is sttpposed they must have been vic- 
tims of a pestilence. 

While stationed upon Angel Island in San Francisco harbor I ob- 
served several migrations of rats between the army post and the quar- 
antine station, which were about a mile apart and separated by an in- 
tervening ridge. Everyone is familiar with the sudden invasion of 
stores, factories, and other structures with these rodent pests, which 
causes considerable economic loss. 

On Vessels. — Eats are found on all vessels; they are great travelers. 
It is through this seagoing tendency that the rat has become cosmo- 
politan. Eats get on board vessels readily as they lie at their dock; 
sometimes they are carried on board in the cargo. 

It is very important to prevent the introduction of rats on vessels 
at plague-infected ports; it is also important to prevent the passage of 
rats from ship to shore, particularly if the vessel is from a plague port. 
In order to accomplish this, it is necessary to exercise particular care. 
In extreme cases the ship should not approach the dock, but the cargo 
should be handled l)y means of lighters. When the ship lies at its 
moorings in a stream or in the open bay rats may get on board by 
swimming, and climbing in through the hawse pipe. Eats rarely swim 
more than one-C[uarter to one-third of a mile. If the vessel ties up at 
the dock, inverted funnels should be placed on the hawsers. The gang- 
planks should be watched during the day and always taken up at night. 
Vessels from plague ports should always be treated with sulphur dioxid, 
preferably when empty, and always before leaving, and also en route, 
to kill the rats that may be on board. A wise measure in international 
sanitation would be to require all vessels, whether trading at plague 
ports or not, to fumigate for rats no less than three or four times a year. 

Food. — Eats are not strictly herbivorous, as might be inferred from 
their dentition; they are practically omnivorous. Their bill of fare in- 
cludes grains and seeds of every kind ; flour, meal, and all food products 
made from them; garden vegetables, mushrooms, bark of growing trees, 
bulbs, roots, stems, leaves, and flowers of herbaceous plants; eggs, chick- 
ens, ducklings, squabs, and young rabbits; milk, butter, and cheese; 
fresh meat and carrion; fish, frogs, mollusks, and crustaceans; they are 
also cannibals. This great variety of food explains the ease with which 
rats maintain themselves in almost any environment. 

Habits. — The roof rat {Mus aUxandrin-us) and the black rat {Mus 

rattus) are more expert climbers than the brown rat, which is larger 

and clumsier. In buildings the brown rat keeps mainlv to the cellar 


and lower parts, where it commonly live? in burrows. From these re- 
treats it makes niglitly excursions in search of food. The roof rat and 
the black rat live in the walls or in tlie space between ceilings and roofs. 
Rats readily climb trees to obtain fruit. In tlie tropics the roof rat 
and the black rat habitually nest in trees. In the open rats seem to 
have defective vision; by daylight they move slowly and uncertainly; 
on the contrary, at the side of the room and in contact with the wall 
they run with great celerity. This fact suggests that the vihrissce 
(whiskers) serve as feelers, and that the sense of touch in them is ex- 
tremely delicate. The animals alwa}^? prefer narrow places as highways 
— another circumstance which may l^e made use of in placing tra])S. 

The ferocity of rats has been grossly exaggerated. The stories of 
their attacks upon human beings, sleeping infants especiall}^ have but 
slight foundation. Ordinarily the probal)iIity of being bitten l)y rats is 
remote, and the bite is not usually poisonous. Miyake ^ has described 
a "rat-bite disease" called Sodoku in Japan. 

Plague in Rats. — It is now known that rats are more or less respon- 
sible for cases of human plague, and in addition are the most frequent 
medium by which plague is carried from one locality to another. They 
also convey the plague infection to other rodents, such as ground squir- 

The clinical manifestations of plague in rats are of little importance. 
It is generally said that a plague-infected rat staggers about with a 
drunken gait, loses fear of its natural enemies, and is readily captured. 
Rats experimentally infected show no marked manifestations of illness 
until shortly before death, when they become quiet, crouch in the cor- 
ner of the cage, and try to hide. It is rather surprising that compara- 
tively few plague rats are found dead in endemic centers. In the San 
Francisco campaign McCoy estimates that certainly not more than 20 
per cent, of the infected rodents were found dead, the remainder being 
trapped. This is probably due to the fact that plague in rats is of 
several days' duration, and during this period there are good chances of 
catching the sick rodent in a trap, while the chance of finding the body 
after death is handicapped by obvious circumstances. 

Rats suffer both with acute plague and chronic plague, the lesions 
of which differ. 

The diagnosis of plague in rats may he made maeroscopically. The 
Indian Plague Commission, which had the opportunity of examining an 
enormous number of plague rats in Bombay and elsewhere in India, state 
that "the results of tests carried out for the purpose of comparison 
make it manifest that the naked eye is markedly superior to the micro- 
scopic method as an aid in diagnosis, and as the result of our experi- 

^ Mitt. a. d. Grensgeh. d. Med. u. Chir., 1902; also Proescher, Internat. 
Clinics, IV, 25th Series, p. 77. 


ence we are prepared to make a diagnosis of plague on the strength of 
the maeroscopical appearance alone, even though the other results of 
cutaneous inoculation and culture are negative and the animals show 
signs of putrefaction." The experience of McCoy and others in the 
Federal Plague Laboratory in San Francisco leads to the same conclu- 
sion. It should be remembered, however, that occasionally plague oc- 
curs in rats without gross lesions. This has been observed by Dunbar 
and Ivister and also by McCoy. In any critical case the bacteriological 
confirmation is essential. 

Acute plague in rats is characterized by engorgement of the subcu- 
taneous blood vessels and a diffuse pink color of the subcutaneous 
structures and muscles. The diagnosis may often be inferred at the 
first incision. The lymphatic glands of the neck, axilla, groin, or pel- 
vis are enlarged and frequently surrounded by a hemorrhagic exudate 
and edema. The liver is granular with focal necroses, the spleen en- 
larged and friable, and j^leural effusions are common. 

Chronic plague in rats has been encountered in a considerable num- 
ber of cases among Mus rattus in the Punjab villages of Kasel and 
Dhand. It has not been foimd in California. In the chronic disease 
the lesions consist of purulent or caseous foci, usually of the visceral 
type; that is, they occur as splenic nodules and abscesses, or mesenteric 
abscesses. Sometimes the abscesses are situated in the regions of the 
peripheral lymph glands. Plague bacilli are either absent or very 
scanty upon microscopic examination in these abscesses, but they may 
be recovered by cultural methods or more surely by inoculating the 
material into susceptil^le animals. There is no evidence to show that 
chronic rat plague has anything to do with the recurrence of acute 
plague among the rats. 

Eats may be infected by the ingestion of infective material or the 
application of virulent plague bacilli to a mucous or cutaneous surface, 
or by subcutaneous injection of the microorganism. The infection may 
also be transferred from rat to rat through the agency of the flea. In 
nature the mode of transference probably takes jolace through all of 
these methods, but commonly through the flea. 

Contrary to the general impression, the wild rat has a considerable 
resistance to plague infection. The Indian Plague Commission found 
that 59 per cent, were immune when inoculated by the subcutaneous 
method from the spleen of infected rats. A series of experiments con- 
ducted in the Federal laboratory in San Francisco also showed a high 
grade of immunity, especially among the large rats. About 15 per 
cent, of small rats and about 50 per cent. of. large rats Avere found to 
be immune when inoculated with highly virulent material. The experi- 
ments demonstrated that this immunity is not acquired through a prior 
attack of the disease, but must be a natural immunity. 


The natural subsidence of plague among rats in any community is a 
point about which much more evidence must be obtained before we can 
speak with any degree of autliority. It may be due to a lack of suscep- 
tible material, ])0ssil)ly to a loss of virulence of the organism, but it 
seems more probable that it is due to a change in the number or rela- 
tions of the ectoparasites of the rat. 

Rat Leprosy. — ^Leprosy occurs spontaneously among rats and bears a 
close reseiubhuu-e to llie disease in man, but it seems that the rat lep- 
rosy is not communicable to man. For a further discussion of rat lep- 
rosy see page 393. 

Trichinosis. — The three most important hosts for the TrichineUa 
spiralis are man, swine, and rats. The infection is spread by one ani- 
mal eating the flesh of another. It is. therefore, evident that if the 
disease occurred only in hogs and man it would soon die out. Rats, on 
account of their habits, may then be viewed as the great reservoir for 
the parasites and for the disease it causes. Hence, a well-directed pub- 
lic health cam])aign against trichinosis should consider the eradication 
of rats, especially around slaughter houses, butcher shops, hog pens, 
and similar places. 

Trichinosis is very common among rats; they become infected by 
eating each other, by eating scraps of pork found on the offal pile of 
slaughter houses, butcher shops, or in swill. Swine become infected by 
eating rats and infected offal. Man becomes infected almost exclusively 
by eating pork or boar meat that has not been thoroughly cooked. 

Other Parasites. — IJats and mice may harbor eleven species of in- 
ternal parasites which also occur in man. Seven of these are of academic 
importance only. Those which concern us principally, in addition to 
the TrichineUa spiralis, are the Tlymenolepis diminuta and Lamhlia 
duodenalis. Rats also harbor the Ci/sticercas celliilosa', and are suscep- 
tible to experimental infections with Trypanosoma gamhiense, the cause 
of sleeping sickness. 

Eats have also been accused of dragging typhoid from the sewers 
to our food. The connection is close and the possiljility apparent. A 
recent outbreak of typhoid fever in an asylum has, in fact, been traced 
to this source by Dr. ]\Iills.'' 

Economic Importance. — The destruction of food, merchandise, and 
property by rats is so great that this alone would justify active measures 
of suppression, even though they were not responsible for plague, trichi- 
nosis, and other infections. Rats destroy grain while growing; invade 
stores, destroy flowers, laces, silks, carpets; eat fruits, vegetables, meat, 
etc., in the market; destroy by pollution ten times as much as they eat; 
cause conflagration by dragging matches into their holes; gnaw lead 
pipes and floors of houses ;• ruin artificial ponds and embankments by 

^Brit. Med. Jour., January 21, 1911. 


burrowing ; destroy eggs and young poultry ; damage foundations, 
floors, doors, piers; in short, they have become the worst mammalian 
pest among us. It is estimated that in the United States alone the 
losses due to rat depredations vary from $35,000,000 to $50,000,000 

Suppression. — The extermination of the rat is hopeless; they are 
very intelligent and cautious. Extermination seems a biological im- 
possibility, for killing off large numbers gives the survivors an easier 
living. Millions of rats have been killed in India, Japan, San Fran- 
cisco, and other places during the recent plague measures without mak- 
ing an appreciable impress upon the numbers remaining. They may be 
exterminated and kept out of a limited area, such as a ship, a granary, 
a stable, a warehouse, a market, or local compound. In the well-built 
residential sections of a city, with concrete walks, asphalt streets, stone 
cellars, and few stables, there are very few rats. In 10 years of resi- 
dence in such a district in Washington I never saw or heard of one in 
the neighborhood. 

The measures for the repression and destruction of rats will be 
considered under: (1) rat-proof buildings, (2) keeping food from rats, 
(3) natural enemies, (4) traps, (5) poisons, (6) domestic animals, (7) 
shooting, (8) fumigation, and (9) bacterial viruses. 

Eat-pkoof Buildings. — This is a measure of first importance in 
the fight against rats. Eats can only gain entrance to a cement struc- 
ture properly constructed through neglect or ignorance. They come in 
through drain pipes if left open; through doors, especially from alleys; 
and through basement windows. Once in, they intrench themselves in 
out-of-the-way places, nest behind rubbish, and are difficult to dislodge. 
The lower parts of the outer doors of public structures, such as markets 
and wharves, should be reinforced with metal to keep the rats from 
gnawing through. Basement windows should be screened and doors 
provided with springs to keep them closed. 

A rat-proof dwelling must have concrete footings and the walls of a 
wooden house should have one foot of concrete between the sheathing 
and lathing. All water and drain pipes should be surrounded with ce- 
ment. Eat holes may be closed with a mixture of cement, sand, and 
broken glass, or sharp bits of crockery and stone. 

Aside from dwellings, the chief refuges for rats in cities are sewers, 
wharves, stables, provision houses, markets, out-buildings, and uninhab- 
ited structures. Modern sewers are highways and not nesting places for 
rats. They find a safe retreat from nearly all enemies under wooden 
sidewalks. In the country it is important to build corn cribs, barns, and 
granaries rat-proof with the liberal use of cement, iron sheeting, or 
galvanized iron netting. 

Keeping Food from Eats. — Well-fed rats mature quickly, breed 


often, and liave large litters. A scarcity of food helps all other sup- 
pressive measures. Garbage and od'al must l)e disposed of so tliat rats 
cannot get at such stuff. Well-covered garbage cans should l)e required 
and the garl)age frequently removed and ])urned. To dei)osit it upon 
the ground anywhere only invites and nourishes rats and other vermin. 
Slaughter houses are centers of rat propagation. The offal is best dis- 
posed of by burning. Care should also be taken as to the disposal of 
remnants of lunches in office buildings and the disposal of organic waste 
generally. Produce in provision stores may be protected with wire cages. 

Natural Enemies. — The natural enemies of the rat are the larger 
hawks, owls, skunks, foxes, coyotes, weasels, minks, dogs, cats, and fer- 
rets. The persistent killing off of the carnivorous birds and mammals 
that prey upon rats has ])een an important factor in the increase of 
these rodents in the United States. "Rats actually destroy more eggs, 
chickens, and game than all tlie wild animals eomljined. 

Traps. — There are many kinds of traps, such as the guillotine, s])ring 
trap, the cage trap, the barrel and pit trap. One of the best is the old- 
fashioned wire cage trap. The rats get in l)ut cannot get out. In ]jlac- 
ing the trap it is advisable to leave a rat in as a decoy. The trap should 
be placed along runways, or the entrance to the trap may be arranged so 
that the rats first have to go through a pipe, as they like to explore 
dark passages. It requires ingenuity to successfully trap rats. They 
are very wary and avoid man-smell. To guard against this the traps 
may be burned and then smeared with the bait, always handling them 
with tongs or properly prepared gloves. Cheese, bacon, grain, and bread 
are the best baits. 

Poisons. — Poisons are objectionable in dwellings, ov.dng to the odor 
of the dead rats. They are of service in granaries, stables, wharves, 
and similar places. Most rat poisons are dangerous to children as well 
as to chickens and other domestic animals, and, therefore, the greatest 
care must be exercised in their use. It requires experience in laying out 
poisons; the old rats are very smart and will refuse the bait unless 
artfully concealed and judiciously placed. 

The principal poisons used for rats are l)arium carbonate, strychnin, 
arsenic, and phosphorus. In several states the law requires that notice 
of intention to lay poison must lie given to persons living in the neigh- 
borhood. Poisons for rats should never be placed in open or unsheltered 
places. For poisoning rats in buildings and yards occupied by poultry 
the following procedure is recommended : I'wo wooden boxes should 
be used, one considerably larger than the other, and each having two 
or more holes in the sides large enough to admit rats. The poisoned 
bait should be placed in the bottom and near the middle of the smaller 
box, and the larger box should then be inverted over the other. Rats 
thus have free access to the bait, but fowls are excluded. 


The cheapest and most effective poison is barium carbonate. This 
may be made into a dough with four parts of meal or flour to one part 
of barium carbonate. A good plan is to spread the barium carbonate 
upon fish, on toasted bread (moistened), or upon ordinary bread and 

Strychnin is effective and may be used by inserting the dry crystals 
in a piece of meat, cheese, or sausage, which is placed in the runways. 

Arsenic is popular; the powdered white arsenic (arsenious acid) 
may be used as described for strychnin or barium; or a stiff dough 
may be made by mixing twelve parts by weight of corn meal and one 
part of arsenic with whites of egg. An old English formula is one 
pound of oatmeal, one pound of brown sugar, and a spoonful of arsenic. 

Phosphorus is an effective and attractive bait. The yellow phosphorus 
in the proportion of one to four per cent, may be mixed with glucose 
or other suitable material. The use of phosphorus is very dangerous on 
account of fire. Eats poisoned with phosphorus may die on the prem- 
ises and decompose, contrary to the statements sometimes made in the 

The following formula is recommended as a poisonous bait for rats, 
mice, squirrels, etc. : 

Strychnin 1 oz. 

Cyanid of potassium 2 oz. 

Eggs 1 doz. 

Honey 1 pint 

Wheat or barley 30 lbs. 

Stir eggs well, then mix in honey and again stir. Then put in dry 
powdered strychnin and cyanid and stir until well mixed. Put wheat 
in large box or can and pour in the mixture of poison and stir until 
it is well distributed over the wheat. Stir two or three times during 
twenty-four hours, then spread out and dry. Before putting it out for 
squirrels add oil of rhodium, 1 drachm. 

Domestic Animals. — A well-trained dog may be relied upon to 
keep the farm premises reasonably free of rats. Small Irish, Scotch, 
and fox terriers make the best ratters; the ordinary cur and the larger 
breeds of dogs seldom develop the necessary qualities for ratters. 

However valuable cats may be as mousers, few of them learn to 
catch rats. The ordinary house cat is too well fed and too lazy to un- 
dertake the capture of an animal as formidable as the brown rat. Koch 
has advised the breeding and distribution of cats capable and willing to 
attack rats. 

Shooting. — Many rats may be shot as they come out to forage about 
sundown. This method is particularly effective in a large building 


which is suddenly overrun with the rodents. The shooting of a numher 
of them upon two or three successive niglits discourages the remainder, 
who leave for some other happier hunting ground. 

Fumigation. — Kats may he killed with certainty in any inclosed 
structure by the use of sulphur dioxid, carbon bisulphid, hydrocyanic 
acid gas, or carbon monoxid. The methods of evolving these substances 
have been described in Section XII. Sulphur dioxid is particularly 
useful to destroy rats on board ships, in cellars, stables, sewers, and 
places where they abound and which are not injured by the corrosive 
action of the sulphur fumes. Enormous numbers of rats are frequently 
killed when ships are fumigated with sulphur dioxid. I have seen buck- 
ets full thrown overboard from comparatively small vessels. Hobdy 
counted 310 on a lumber-carrying schooner of only 260 tons burden. 
The S.S. Minnehalia, a new vessel only nine months in commission 
fumigated in London in May, 1901, yielded a bag of 1,700 rats. 

For the destruction of rats upon vessels the sulphur dioxid may be 
produced by the pot method, if the hold is empty, or may be generated 
in a Kinyoun-Francis or a Clayton furnace, or may be liberated from 
its compressed liquefied state. No less than three pounds of sulphur 
should be burned for each 1,000 cubic feet of space, and the exposure 
should not be less than 5 hours (see page 997). 

Carbon Monoxid. — Carbon monoxid is an exceedingly poisonous gas. 
From the fact that it has no odor it is even more hazardous in practice 
than hydrocyanic acid. Carbon monoxid is fatal to all forms of mam- 
malian life, but has no germicidal properties whatever. It has been 
used in Hamburg ^ and other ports for the destruction of rats on ships. 

Carl)on monoxid is a colorless, odorless gas, lighter than air. It 
forms a stable compound with the hemoglobin of the blood — carl)on 
monoxid-hemoglobin. For the toxic action of this gas and its other 
properties see page 637. The particular advantages of carbon monoxid 
for the destruction of rats on hoard ship are that it may be generated 
cheaply, is quickly effective, and does no injury to cargo or vessel. The 
disadvantages are that it is poisonous and inflammable. The addition 
of a little sulphur dioxid to the gas makes its presence known and tends 
to prevent accidents. After exposure the hold must be thoroughly ven- 
tilated, and it is customary to lower a mouse in a cage for 10 minutes 
to be sure that it is safe for a man to enter. Divers' helmets should 
also be kept in readiness so that the hold may be entered in case of 

A gas generator has been made by Pintch which furnishes a mix- 
ture consisting of CO, 5 per cent., CO2, 18 per cent., N", 77 per cent. 
These gases are generated by the incomplete combustion of coke. The 

*Nocht*and Giemsa: Arbeiten a. d. kaiserlichen Gesundheitsampte, Bd. 20, 
Ersten Heft, 1904, p. 91. 


mixture of gases is pumped into the hold of the vessel or other com- 
partments where it is desired. The hold should be kept tightly closed 
from 7 to 8 hours. 

The Bacterial Eat Viruses. — Eats are notoriously resistant to 
bacterial infection.^ Even plague usually fails markedly to diminish 
their prevalence. An epizootic of bacterial nature, therefore, cannot be 
classed with the natural enemies of the rat. We are not surprised, then, 
to learn that the bacterial rat viruses have signally failed to accomplish 
their mission. 

These bacterial viruses belong to the colon-typhoid group of organ- 
isms. They are either identical with or closely related to the original 
bacillus of mouse typhoid {B. typhi murium) discovered by Loeffler, or 
the paratyphoid bacillus, type B, which is frequently the cause of meat 
poisoning, or the Bacillus enteritidis of Gaertner, which has been asso- 
ciated with gastrointestinal disorders. 

The claim that these rat viruses are harmless to man needs revision, 
in view of the instances of sickness and death reported by various ob- 
servers. The pathogenicity for man depends upon the virulence of the 
culture, the amount ingested, the nature of the medium in which it 
grows, and many other factors. 

Danysz virus (B. typhi murium) is pathogenic for rats under labora- 
tory conditions, but has feeble powers of propagating itself from rat to 
rat. It rapidly loses its virulence, especially when exposed to light 
and air. The result depends largely upon the amount ingested. The 
other viruses have proven even less satisfactory. 

Under natural conditions these rat viruses may be likened to a 
chemical poison, with the great disadvantage that they rapidly lose their 
virulence and arc comparatively expensive. They also have the further 
disadvantage that chemical poisons do not possess of rendering animals 
immune by the ingestion of amounts that are insufficient to kill or by 
the ingestion of cultures that have lost their virulence. 

Squirrels. — In August, 1903, a blacksmith died of plague probably 
contracted from a squirrel in Contra Costa County, California. In 
1904 Currie demonstrated the susceptibility of the ground squirrel to 
bubonic plague. In 1908 McCoy and Wherry discovered natural plague 
in ground squirrels. It was then learned that thousands of squirrels 
had died of some disease during 1904, 1905, and 1906. This epizootic 
was doubtless plague. It is now realized that plague has become en- 
demic in California, in the squirrel. It is also believed that the 
disease has been kept alive in the endemic foci of Tibet in an- 
other rodent, the marmot (Arctomys hohac). The eradication of plague 

^ ' ' The Inefficiency of Bacterial Viruses in the Extermination of Eats, " M. J. 
Eosenau. "The Eat and Its Eelation to the Public Health," Bulletin of the 
P, H, & M. H. S., 1910, 


must, therefore, consider these and perhaps other susceptible wild 

California is overrun with three species of ground squirrels. The 
commonest is the CiicUus heecheyi. Thev live in colonies in burrows 
or warrens. The booby owl is. a frequent companion occupying the same 
burrow, and they probably spread the infection by carrying fleas. Squir- 
rels become infected through fleas from each other and from rats. The 
squirrel flea (Ceratopliijllus acidus) attacks num just as the rat flea 
does. The infection may also be conveyed to man through sciiiincl bites, 
as in the case of the child in Los Angeles studied by Stimson. Squir- 
rels make good food for man, but since the danger has been realized 
the shooting or trapping of them for food purposes is now forbidden 
in California. 

Plague in the squirrel may be recognized ' by the gross anatomical 
lesions in the lymphatic glands, the liver, and lungs. The pneumonic 
form of the disease is common in the squirrel. Many cases are subacute 
or clironic. Smear preparations from squirrels dead of plague are 
frequently negative for plague-like bacilli. The diagnosis may, there- 
fore, be made more surely by animal experimentation. Subcutaneous 
inoculation is surer than the cutaneous method, as the latter often 
fails on account of the comparatively few plague bacilli present in squir- 
rel lesions. 

Squirrels may be destroyed by various means. One of the most 
successful is to saturate cotton waste the size of an orange with carbon 
bisulphid and place it in the warren; then close the opening with wet 
clay. Poisoned bait, such as strychnin, phosphorus, or cyanid of potas- 
sium, is effective. Traps are not very successful, as the squirrel is 
wary. Natural enemies, such as the coyote, wolf, badger, skunk, moun- 
tain lion, the cobra snake, and red-tailed hawk should be encouraged.^ 


In considering the prevention of plague it is necessary to recog- 
nize that the different types of the disease are spread in different 
ways. At least three clinical types are now recognized: (1) bubonic, 
(2) pneumonic, and (3) septicemic.^ In the bubonic and septicemic 
types of the disease the plague bacillus is locked up in the glands, 
blood, and other tissues and organs of the body, and are not eliminated 

'McCoy: Jour, of Infect. Dis., Nov. 26, 1909, Vol. V, No. 5. 

^ In this chapter material has been freely drawn from ' ' The Rat and Its 
Relation to the Public Health," Public Health and Marine Hospital Service, 
1910, particularly articles by Lantz, McXJoy, Brinckerhoft", Banks, Stiles. Rucker, 
Creel, Holdy, Kerr, and Rosenan. This book may bo obtained by addressing the 
Surgeon-General or the Superintendent of Public Documents, Washington, D. C. 

^Occasionally other varieties occur in which the chief manifestations are in 
the skin and subcutaneous tissues, or in the intestines, causing diarrhea. In the 
latter case the infection is' excreted in the feces. 


in the usual excretions. These forms of the disease are, therefore, not 
'^contagious," but are spread mainly through the agency of the ilea. 
On the other hand, in the pneumonic type of the disease plague bacilli 
are contained in enormous numbers in the sputum. The disease is 
frequently transmitted directly by close association with a patient hav- 
ing plague pneumonia. The pneumonic type of the disease does not 
necessarily follow when the infection is taken into the system through 
the respiratory channel; on the other hand, it may result from infection 
through a flea bite. 

The Bacillus pestis (Yersin, 1894) has more than fulfilled Koch's 
laws. Several accidents in which pure cultures have been inoculated 
into man, producing all the symptoms and lesions of the disease, have 
added to the proof that this organism is the cause of plague (Vienna, 
1898, Ann Arbor, 1902, and also in laboratories in Eussia, Berlin, and 
Japan). The plague bacillus is comparatively easy to isolate and grows 
readily on artificial culture media, and has characteristics that readily 
distinguish it from all other species. It is a short rod with rounded 
ends, not motile, decolorized by Gram's method, and grows better at 
30° C. than at blood temperature. 

Eecognition of the plague bacillus rests upon the following charac- 
teristics: (1) Curious involution forms upon salt agar within 24 hours; 
(2) stalactite growth in liquid media; (3) characteristic lesions pro- 
duced by experimental plague in guinea pigs, rabbits, rats, etc. Kolle's 
method consists in rubbing the material containing the plague bacillus 
upon a shaved area of the skin of a guinea pig. The plague bacilli pene- 
trate the skin, leaving other pathogenic organisms behind. The skin of 
the guinea pig thus acts as a differential filter; (4) the final test of the 
identity of the plague l^acillus is the fact that its pathogenicity may be 
neutralized by the use of antiplague serum. 

The Bacillus pestis does not live a saprophytic existence in nature. 
It is readily killed by drying, sunlight, heat, and the usual germicides. 
The organism does not live long in the soil or upon the floors of houses, 
as was once commonly supposed. There is, therefore, comparatively 
little danger from these sources. 

Immunity. — One attack of plague usually protects for life. Occa- 
sionally second attacks are noted in the same person. In such cases 
the second attack is usually mild. This is an old observation and led 
to the employment of persons with a plague history or a plague scar 
in hospitals and laboratories. 

Artificial immunity of either an active or passive nature may be 
acquired by various procedures. The passive immunity produced by 
the injection of antiplague serum lasts only about three to four weeks. 
The active immunity produced by vaccination of cultures may be de- 
pended upon for about six months. 


Ilafflxine's prophylactic consists of a killed culture of the pla^e 
bacillus, which is injected subcutaneously. HafPkine used a bouillon 
culture, six weeks old, grown at 25-30° C. and killed at 65° C, for 
one hour. One-half of one per cent, of phenol is then added. From 
2 to 3.5 c. c. (this was later increased to 20 c. c.) of this vaccine are 
injected subcutaneously. Ten days later a second injection of a still 
larger amount is given. 

In twelve districts in India 224,228 persons were inoculated with 
Haffkine's prophylactic. Of these 3,399 took the disease. Of 639,600 
not inoculated in the same districts 49,430 were attacked. C. J. ^Martin 
concludes that the chances of subsequent infection are reduced four- 
fifths, and the chances of recovery are 2.5 times as great as in the cases 
of the non-vaccinated. 

The German Plague Commission prepared their prophylactic vac- 
cine from a fresh virulent agar culture, suspending the bacilli in salt 
solution or bouillon. The organisms are killed at 65° C. for one to 
two hours, and 0.5 per cent, phenol added. The amount injected rep- 
resents one agar culture. 

Lustig and Galliotti extract the immunizing substance from the 
bacterial cell (endotoxin) with weak potassium hydroxid. This nucleo- 
protein is collected and dried, and thus permits of exact dosage. The 
amount injected is two to three milligrams of the dry extract dis- 
solved in water. 

Terni and Bandi recommend the peritoneal exudate of plague- 
infected guinea pigs, sterilized fractionally at 50° C. and the addition 
of 0.5 per cent, of phenol, 0.25 per cent, sodium carbonate, and 0.75 
per cent, sodium chlorid. 

Shiga prefers a combined active and passive immunity produced 
with killed cultures and antipest serum, because this mixed immu- 
nizing process has the advantage of producing milder reactions. 

Kolle and Strong started out from the principle that a much higher 
degree of immunity is produced by living microorganisms than dead 
ones, and recommend the use of live attenuated cultures. Strong has 
a strain, an entire agar culture of which may be injected into man 
without harm. In ^Manila 42 persons were given a preventive inocula- 
tion with this culture. 

The reactions which follow vaccination with a plague culture, 
whether alive or dead, are sometimes marked. The symptoms consist 
of a rise in temperature to 39° C, malaise, depression, and headache, 
and swelling and pain at the site of the inoculation. The symptoms 
usually pass away in 24 to 48 hours. 

The production of an active acquired immunity has a distinct prac- 
tical usefulness in the prevention of the disease, although it cannot take 
the place of rat and flea eradication. It has been used on a large 


scale by Haffkine in India, and to a lesser extent by others in many 
parts of the world during the recent plague pandemic. Those who 
get plague after Haffkinization usually have a mild form of the dis- 
ease, which, in the experience in India, rarely results in death. The 
active immunization of the community in the face of an epidemic 
is a valuable addition to our preventive measures against plague. 
It is of first importance in jDrotectiug small communities, on ship- 
board, in camps and barracks, at quarantine stations, in plague labora- 
tories, among rat brigades, as well as for physicians, nurses, and others 
who are exposed. 

Yersin's serum is obtained from a horse that has received repeated 
injections of plague cultures; at first killed plague cultures, afterward 
living bacilli, are used. At most this antitoxic serum is weak, and, 
while it has a certain amount of protective properties, it has slight 
curative power. Very large quantities must be administered early in 
the disease to obtain any effect at all. The protection lasts only a few 
weeks, three to four at most, and is, therefore, of limited practical use. 

Endemic Foci. — There are four historic endemic foci in which plague 
has slumbered for ages. One is on the eastern slope of the Himalayas, 
in the valley of the Yiinnan. The great epidemic in Hongkong in 1894 
came from this center. A second endemic focus near, and perhaps con- 
nected with the first is on the western slope of the Himalayas. From 
here the infection was carried to Bombay in 1896, where it still prevails. 
A third plague focus exists from about the center of Arabia to near Meso- 
potamia. From here the infection was dragged to Samarkand, the Black 
Sea, and Persia. The fourth endemic area was discovered by Koch in 
1898 in the interior of Africa, near the source of the- White Nile in 
Uganda. We must now add to this a fifth endemic focus, for plague has 
obtained a foothold in California in the ground squirrels, which will 
take years of well-directed energy to control. The disease has caused 
dreadful havoc in India since 1892. In 1907 over one million persons 
died of plague in that country. 

Plague is kept alive in the endemic foci in the rat, the ground 
squirrel, the marmot, the brush rat, and other rodents. The campaign 
of eradicating plague in the ground squirrel in California has been 
directed to killing as large a number of these animals as possible. For 
this purpose carbon disulphid, sulphur dioxid, hydrocyanic acid gas, 
bait poisoned with strychnin, and cyanid of potassium are used. Natu- 
ral enemies, such as the coyote, wolf, fox, badger, snake, mountain 
lion, skunk, and red-tailed hawk, are encouraged. Trapping has not 
proven successful, as the squirrel is a very wary animal. Many squir- 
rels may be shot, but those killed should not be used for food. 

Management of a Plague Epidemic. — The handling of a plague 
epidemic is conducted along two definite lines of activity. One is to 


liml and care for the luiinan cases, the other consists in a warfare 
aijaiiist rats. The organization and general management of a phigiie 
campaign do not diil'cr radically from similar work in other epidemics 
(see page 319). Cases of the disease must be sought for and early 
diagnosis coniirmcd; all deaths from no matter what cause must be 
investigated, and the body examined by an expert before burial is per- 
mitted. A bacteriological laboratory is a sine qua non. Cases of the 
disease should be isohitcd and the usual disinfection of excreta and 
surroundings exercised. Particular care must be taken that the isola- 
tion wards are vermin-frco. The place from which the case is removed 
should then be given a preliminary disinfection with sulphur dioxid 
or other substance that may be depended upon to kill rats and fleas, 
and a search made in the neighborhood for secondary cases both in 
man and rodents. 

The campaign against the rat is expensive and dilTicult, but must 
be vigorously prosecuted to insure success. The rat warfare may be 
briefly summarized as a simultaneous attack upon the habitation and 
food supply of the rat; the destruction of rat burrows and nesting 
places; the separation of the rat from his food supply by concreting and 
screening such places as stables, warehouses, markets, restaurants, etc.; 
the prevention of the entry of the rat into human habitations by the 
use of concrete, wire netting, or other barriers ; and the use of poisons, 
traps, etc. For further con'^ideration concerning rats and their eradi- 
cation see page 242. All the rats that are caught in traps or found 
dead are brought to the bacteriological laboratory, where tliey are ex- 
amined and careful records kept concerning the species, the location, 
the place where the rat was caught, the character of the infection, etc. 
As it is a hopeless task to exterminate rats from a large city, Ileiser 
has jjroposed a practical plan which proved effective in j\Ianila. A 
list of the places in which the plague-infected rats were found was 
made. Each was regarded as a center of infection. Eadiating lines, 
usually five in number, were prolonged from this center, evenly placed 
like the spokes of a wheel. Rats were caught along these lines and 
examined. Plague rats were seldom found more than a few blocks 
away. The furthermost points at which the infected rats were found 
were then connected with a line, as is roughly shown in the diagram. 
Figs. 38 and 39. The place inclosed by the dotted line was regarded as a 
section of infection. The entire rat-catching force was then concen- 
trated along the border of the infected section, that is. along the dotted 
line. 'I'hey then commenced to move toward tlie center, catching the 
rats as they closed in. Behind them ratproofing was carried out. One 
section after another v/as treated in this way, until they had all been 
wiped out. Once weekly thereafter rats were caught in the previously 
infected sections and at other places, especially those which had been 



infected in years gone by. Since the above system was adopted plague 
has disappeared in the city of Manila, and at a cost of only a small 
fraction of that of a general rat extermination campaign. 

Quarantine. — Plague infection is frequently carried over seas in 
vessels. When this happens it is more apt to be due to the disease in 
the rat than man. Maritime quarantine, therefore, finds its greatest 
justification in keeping out plague. To be successful, measures must 
be directed almost entirely against the rat, although a keen eye must 

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be kept on the lookout for mild cases known as Pestis minor, or walk- 
ing plague. Rats may be kept down on board a vessel by the frequent 
use of sulphur dioxid. All vessels trading with a plague-infected port 
should have each cargo compartment fumigated with this gas, at least 
when it is empty, at the port of departure. The vessel must be again 
fumigated with sulphur dioxid on arrival. Both at the infected port 
and at the port of arrival care must be taken to prevent the ingress 
and egress of rats. The period of detention of the personnel for a 
plague ship is seven days. For further details concerning quarantine 
see page 321. 



Prevention — Summary. — The principles and many of the details for 
the prevention of plague have been stated in the foregoing pages, and 
need not be repeated. 

Personal prophylaxis consists in avoiding the infected regions and 
guarding against flea bites. Physicians and nurses should remember 
that the pneumonic form of the disease is higlily "contagious" in the 
ordinary sense of the term. Attendants and persons who come in con- 
tact with such cases may protect themselves with Haffkine's prophylac- 
tic or Ycrsin's serum. Individual measures to guard against droplet 

Fig. 43. — Isolated Plague-infested Center, Manila, P. I. 

infection, such as the wearing of masks or veils of cheesecloth, may 
be resorted to. The bubonic and septicemic forms of the disease are 
not, as a rule, directly communicable, and, therefore, the preventive 
measures recommended for typhoid fever are effective. 

The ordinary germicidal solutions, such as bichlorid of mercury, 
1-1,000, carbolic acid, 2i/^ per cent., formalin, 10 per cent., are effec- 
tive against the Bacillus pestis. Of the gaseous disinfectants sulphur 
dioxid is preferred, because it not only kills the frail plague bacillus, 
but also destroys rats, fleas, etc. 

Cases of plague should be isolated in a well-screened room other- 
wise free of insects. Fabrics and other objects which become contam- 

TICKS 261 

inated with the discharges should be thoroughly disinfected by proper 

It is important to have prompt reports of all cases of suspected 
plague, and the diagnosis must be confirmed by bacteriological meth- 
ods. In all plague centers there should be a special hospital and also 
a laboratory where diagnostic work may be carried on; this is an es- 
sential part of the equipment for a successful campaign. A traveling 
laboratory organized like a flying squadron for quick service should 
be provided to furnish this service wherever it may be demanded. 

The prevention of plague, after all, is reduced to warfare against 
rats and fleas. This has been fully discussed. All seaport towns hav- 
ing communication with plague countries would do well to examine 
for plague rats caught from time to time about the wharves. This, 
in fact, should be one of the routine duties of the port sanitary authori- 
ties. Plague may slumber in the rats for years before human cases 
occur. Other preventive measures are obvious from the nature of the 
infection and its mode of transmission, or have already been stated in 
the preceding pages. 


Ticks belong to the family Ixodidse, and the diseases which they 
transmit are known as isodiasis. Quite a number of different species 
are known to attack man. 

Ticks, or wood lice, are not true insecta, but belong to the acarines 
which include the mites, and are closely allied to spiders and itchmites 
(scabies). Ticks have an unsegmented body with eight legs in the 
adult stage and six legs in the larval stage. In some of their habits 
they resemble bedbugs. So far as is known, they take no vegetable 
food, but live on blood. Ticks are ectoparasites of man and many 
animals. They frequently hang tenaciously to the skin, in which 
they partly bury themselves. If covered with oil or vaselin, thus clos- 
ing their breathing pores situated behind the fourth pair of legs, they 
may be induced to release their hold. If pulled off roughly the head 
(capitulum) is likely to break off and remain in the skin. Sulphur 
in some form is useful to destroy ticks in the adult stage. Sulphur 
ointment is particularly obnoxious to this group of parasites. Ar- 
senic and crude oil also act as poisons to the tick, and may be used 
by local application. 

The life cycle of the tick consists of four distinct stages, viz. : egg 
(embryo), larva, nymph, and adult. The eggs are invariably deposited 
on the ground in large masses. The larvas which emerge from the 
eggs are minute six-legged creatures. The larvse attach themselves to 
a suitable host, upon which they feed, then usually drop to the ground 


and molt, becoming nymphs. The nymphs have eight legs. The nymph 
waits until it can attach itself to a liost. engorges blood, usually drops. 
molts its skin, and becomes adult. The life history of the tick 
differs from the mosquito in that the larval and pupal stages are not 

It was first shown by Smith and Kilborne that in the case of Texas 
fever the microorganism within the adult tick passes into the egg and 
is, therefore, transmitted "hereditarily" to the next generation. The 
infection of Eocky Mountain spotted fever, of canine piroplasmosis. and 
probably also that of African tick fever, is also transmitted by the female 
to the next generation. Tick-borne diseases are not always transmitted 
in nature in this way. The virus may be transferred directly by the 
larva, the nymph, or the adult. Thus some ticks leave their host re- 
peatedly, and the parasites they draw from one animal may be injected 
into another animal either during the same or at a subsequent stage in 
the development of the tick. 

Ticks upon domestic stock may be controlled by dipping, spraying, 
or by hand methods. The arsenical dip has practically displaced all 
others for the destruction of ticks in the various parts of the world. 
Crude oils have been used to a considerable extent in some cases. They 
are more expensive than the arsenical dip, and dangerous to cattle 
under some conditions. Serious losses have followed the use of heavy 
oils in dry regions, or where it has been necessary to drive the cattle 
any considerable distance after dipping. 

The formula for the arsenical dip is as follows: 

Sodium carbonate (sal. soda) 24 lbs. 

Arsenic trioxid (white arsenic) 8 lbs. 

Pine tar 2 gals. 

Water sufficient to make 500 gals. 

Sometimes dipping is not practical. Instead of driving cattle con- 
siderable distances to dipping vats it will be found sufficient to treat 
them thoroughly by hand methods. The procedure consists simply in 
applying the arsenical mixture liberally by means of rags, mops, or 
brushes, or by means of spray pumps. Crude oil may be used by hand 
instead of the arsenical solution. For most tick-borne diseases cattle 
must be dipped or treated weekly. 

The following diseases transmitted by ticks will be given brief con- 
sideration: Texas fever (Margarojnis annulatus). South African tick 
fever {Ornithodoros savignyi), Eocky Mountain spotted fever {Derma- 
cenfor venustus), and relapsing fever (Ornithodoros moubata). Al- 
though it is probable that the latter disease is also transmitted by the 
Argas persicus, and perhaps other biting insects. 

TICKS 263 


Texas fever or splenetic fever is also known as bovine malaria, tick 
fever, and hemoglobinuria. The disease does not affect man. It is 
confined to cattle, and is of very great economic importance. Texas 
fever is an infection which should be understood by all sanitarians, on 
account of its scientific and historic importance. The cause of this in- 
fection and its mode of transmission were ascertained in 1893 by Smith 
and Kilborne. The discovery that the tick is the intermediate host of 
Texas fever opened an entirely new principle in the sanitary sciences. 

Texas fever is caused by a protozoon parasite. This parasite was 
first named Pyrosoma higeminum on account of the twin-like, pear- 
shaped forms commonly seen in the red corpuscles. This genus was 
changed by Patton in 1895 to Piroplasma. These terms having been 
preoccupied, the present name of the parasite is Babesia higemina.^ 








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Fig. 44. — The Tkxas Fever Tick (Margaropus annalatus). 

The contagium is carried by the cattle tick, Boophilus hovis, now 
M. annulatus. The tick lives upon the skin and feeds upon the infected 
blood, becomes sexually mature at the last molt; the female drops to 
the ground and lays about 2,000 eggs; the newly hatched larvae attach 
themselves to the skin of a fresh host, which they infect. This explains 
the long extrinsic period of incubation in this disease, 40-60 days; 30 
days of which are required for the development of the larvae and the 
remainder for the development of the parasite within the host. 


This disease, also called tick fever and spotted fever, is an interest- 
ing infection which occurs chiefly in the Bitter Root Valley of Montana, 
centering around Missoula. Cases also occur in the neighboring states 

^ These various names are given for the reason that they are all found in the 



of Idaho and Wyoming. The symptoms closely resemble those of ty- 
phus fever, including a petechial eruption. Anderson and Goldberger 
have shown that typhus fever of Mexico, called tabardillo, is not trans- 

FiG. 45. — Rocky Mountain Spotted Fever Tick. (Dermacentor venustus). 
1, Adult female, unengorged, dorsal view; 2, Adult male, dorsal view; 3, Adult female, 
unengorged, ventral view; 4, Adult male, ventral view; 5, Adult female in act of de- 
positing eggs. 

missible to guinea pigs, while Eicketts and also King independently 
demonstrated that some of the infected blood of a case of Eocky Moun- 
tain fever injected into a guinea pig will reproduce the chief features 
of this disease. The two diseases are, therefore, distinct. 

TICKS 265 

Wilson and Chowning first suggested that the tick acts as the car- 
rier of Eocky Mountain spotted fever. This was proven by Eicketts in 
1906, who showed tliat the particular tick is Dermacentor occiden- 
talis (now venustus). The infection may be transmitted by the larva, 
the nymph, and both the adult male and female ticks. The infection 
is also transmitted hereditarily through the ticks to their larvae. The 
disease has been transmitted through the tick from man to monkey 
and the guinea pig, and also from monkey to monkey and from guinea 
pig to guinea pig. A few infected ticks have actually been found by 
Eicketts in nature. 

Mayer ^ has proved by experiment that different species of ticks col- 
lected from various regions [Dermacentor marginatus (Utah), Amtly- 
omma americanus linnceus (Missouri), and Dermacentor variabilis 
(Mass.)] are able to transmit the virus of Eocky Mountain spotted 
fever. The inference is that the disease may find favorable conditions 
for its existence in localities other than those to which it is now limited. 

One attack of the disease establishes a rather high degree of immu- 
nity to subsequent attacks. The blood serum of recovered cases con- 
tains protective properties of a rather high degree for guinea pigs. 
The virus is not filterable through a Berkefeld filter. The nature of 
the virus is not known. 

The prevention of Eocky Mountain spotted fever is directed en- 
tirely against the tick. Ticks are to be avoided in the infected region. 
If it is necessary to work in the fields and woods and about animals 
where these ticks abound, the bites should at once be cauterized with 
strong carbolic acid. A vigorous campaign should be carried on by the 
health authorities to destroy all the ticks in and about each case of 
the disease. 

The ultimate control of Eocky Mountain spotted fever depends upon 
the suppression of the Dermacentor venustus. This, perhaps, is not so 
hopeless a task as may at first seem likely.- Henshaw and Birdseye ^ 
found twenty species of five hundred mammals examined in and around 
Bitter Eoot Yalley to carry ticks either in the immature or adult stage. 
The mammalian hosts of fever ticks fall naturally into two groups : 
those that harbor chiefly adult ticks and those that harbor the younger 
stages. In the former class belong mountain goats, bears, coyotes, badg- 
ers, woodchucks, and possibly elk, deer, mountain sheep, rabbits, and 
domestic stock, such as horses, cattle, and sheep. Those of the second 
class harboring the nymphs and larvae 'are mainly rodents and comprise 
ground squirrels, woodchucks, chipmunks, pine squirrels, mice, and 

"^Jour. Infect. Bis., April 12, 1911. 

'^ Fortunately the Derm-acentor venustus is the only tick in the endemic region 
which attacks man. 

^ U, S. Dept. of Agr., Bureau of Biol. Survey, Cir. 82. 


wood rats. These smaller animals are too agile to permit the adult 
ticks to remain upon tliem. 

Unquestionably the great bulk of fever ticks {Derma^enior venus- 
tiis) which become engorged in the Bitter Root Valley do so on do- 
mestic stock — horses, cattle, sheep, and sometimes dogs. They ob- 
tain the ticks from the pastures and other uncultivated land infested 
by wild animals. It is obvious, therefore, that, if the domestic ani- 
mals in the valley are rendered tick-free by dipping, spraying, or by 
some other equally effective method, the chances of the infection of 
human beings will be vastly lessened. Dipping carried on upon an exten- 
sive scale throughout the endemic area by McClintic has given surpris- 
ingly successful results, there having been fewer cases of the disease 
this season in the Bitter Eoot Valley than for any year of record. 

Supplementary measures for the control of Eocky Mountain spot- 
ted fever consist in the reduction of the number of rodents and the 
clearing of the brush land along the edges of the valley.^ 

]\IcClintic infected Rhesus monkeys and guinea pigs with spotted 
fever and treated them with the following drugs: salvarsan, sodium 
cacod3-late, and urotropin. The results obtained, however, do not in- 
dicate that any of these drugs possess any value whatever either as a 
prophylactic or in the treatment of spotted fever, but, on the contrary, 
their administration seems on the whole rather to intensify the severity 
of the disease in the animals compared with the course of the disease 
in the controls. - 


Relapsing fever, also called famine fever and seven-day fever, is 
found upon all the five continents of the globe. Epidemics of this 
disease have been reported, especially from Ireland and Russia. The 
infection prevails in India, w^here Vandyke Carter of Bombay made his 
classic investigations. Relapsing fever was epidemic in jSTew York and 
Philadelphia in 1869. It has not reappeared. The disease has receded 
from civilization where cleanliness is observed. 

Obermeier in 1868 discovered the spirillum in the blood — Spirillum 
ohermeieri. Carter and Koch in 1878 showed that the infection may 
be transferred to apes by the inoculation of the blood of a patient. 
Miinch and Moczutkowski transferred the disease by the inoculation of 
relapsing fever blood to healthy individuals. Koch succeeded in dem- 
onstrating that the spirochetes of African relapsing fever multiplied 
in the tick (Ortiithodoros mouhata), and that the bite of this tick 
may convey the disease to healthy men. The African relapsing fever 

'Hunter. W. D., and Bishopp, F. C: "The Rocky Mountain Spotted Fever 
Tick," Bureau of Entomology BuU. No. 105. U. S. Dept. of Agr. 
=^17. S. Pub. Health Beports, Vol. XXVII, No. 20, May 17, 1912. 

TICKS 367 

which Koch studied in East Africa shows some slight diiJerences from 
the European disease. 

Although' Koch and also Button and Todd demonstrated that the 
African relapsing fever may be transmitted through the bite of a 
tick^ it is very probable that in Europe and other countries where re- 
lapsing fever occurs the disease may also be transmitted by the Argas 
persicus. In fact, other insects, as bedbugs, fleas, biting flies, and lice, 
may convey the infection. 

Leishman ^ has demonstrated that the Spirochceta duttoni may be 
transmitted hereditarily in the tick. He has obtained positive results 
in the second generation, the bites of which were infective for mice 
and monkeys. Attempts to carry the infection to the third generation 
in the tick have so far failed. Leishman considers the hereditary trans- 
mission of the infection as biological evidence that the spirochetes be- 
long to the protozoa rather than the bacteria. 

Schuberg and Manteuf e ^ found that a temperature of 22° C. is 
not favorable for the spirochete in the Ornithodoros mouhata. This 
was shown by experiments upon rats in which the infection through 
the bite of the tick disappeared more quickly at 22° C. than at higher 

One attack protects against subsequent attacks. Second attacks 
among negroes in Africa in after years are very light. The only sus- 
ceptible animals are man, the apes, mice, and rats. 

The prevention of relapsing fever is based upon personal and domes- 
tic cleanliness and the avoidance of tick and other bug bites. Personal 
prophylaxis depends upon keeping aloof from vermin-infested places, 
especially where the disease prevails. Manson suggests that a mosquito 
net, a bed well off the ground, and a night light are indispensable in 
Africa, where the nocturnal habits of the Ornithodoros mouhata ren- 
der the hours of sleep especially dangerous. 


This is a febrile disease common in parts of Africa. The incubation 
is from five to ten days and the attack lasts from two days to a week 
or more, with abdominal pains, chills, vomiting, diarrhea. Eelapses 
do not occur as in relapsing fever. The disease is caused by a spirillum 
very similar to the Spirillum ohermeieri, but shown by ISTovy and others 
to have slight differences. The spirillum was demonstrated ' in 1905 
by Button, who also showed that the infection can be transferred to 
monkeys by the bites of young ticks at their first feeding after hatching 
from infected parents. Here again is an instance of the hereditary 

"■Lancet, Jan. 1, 1910, Vol. 1, p. 11. 

^ Zeitsclir. f. Immunitdtsforschung, Orig. Bd. 4, 1910, p. 512,. 


transmission of the parasite in the insect host. Button accidentally 
inoculated himself through a wound on the hand at an autopsy and 
developed the disease which caused his death. 

The particular tick in this case is the Ornithodoros savignyi. The 
prevention of the disease depends entirely upon a knowledge of the 
biology of the tick and efforts to guard against its bite, to prevent in- 
fection of the ticks, and to destroy them, as far as possible, in the in- 
fected regions. 


The insects known as pediculi or lice are parasitic during their 
entire life on warm-blooded animals, including man. They are de- 
graded, flat, rather elongate, wingless insects with a small head and 
stout legs which end in a strong claw, opposable to a projection at 
the tip of the penultimate joint. The mouth parts are of a very pe- 
culiar nature. There is a short beak or proboscis in front. Through 
this beak extends a slender stylet which has three parts. The stylet 
is used to pierce the skin of the host and the blood is thus sucked up 
through the proboscis. Lice usually walk sideways, but do not travel 
much and keep fairly close to one host. The eggs are slightly elongated 
and fastened to the hair of the host or clothing. They hatch in about 
ten to fifteen days, the young coming out of the top of the egg. These 
young do not differ much in structure from the adults, but are paler 
in color. They molt their skin a few times, probably four, before they 
reach the matured condition. The males are less numerous than the 
females, and ordinarily smaller. There are several generations each 
year, dependent, doubtless, on the temperature, but the life history is 
not thoroughly known for any species. 

It is the blood-sucking habits of lice which render them dangerous 
parasites and capable of transmitting disease from one host to another. 
Fortunately, they do not readily change hosts, so that they cannot be 
considered quite as dangerous as some more active parasites. There 
are about 50 or 60 known species which are arranged in 15 genera 
and 4 families. It is Pediculus vestimenti, the clothes or body louse, 
which is mainly responsible for the transmission of typhus fever. 

Three species of lice are found upon man: (1) Pediculus capitis 
(now humanus), the ova of which are attached to the hairs and can 
readily be seen as white specks, known as nits. (2) Pediculus vesti- 
menti (or corporis), the clothes or body louse, lives on the cloth- 
ing, and in sucking the blood causes minute hemorrhagic specks, com- 
monly about the neck, back, and abdomen. (3) Pediculus (or 
Phthirius) pubis or crab louse is found in the parts of the body cov- 
ered with short hairs, as the pubes; more rarely the axilla and eye- 

LICE 269 

The prevention of lousiness is almost entirely a matter of personal 
cleanliness. However, the most scrupulous individuals may become 
infested. Lice may be passed directly from one person to another, or 
occasionally may be carried by flies, or other means. Beds in hotels 
and sleeping cars are sources of infection. 

Human lice may be destroyed with kerosene, turpentine, carbolic 
acid (1-50), bichlorid of mercury solutions, tincture of cocculus in- 
dicus, and other well-known insecticides. It is comparatively easy to 
destroy the adult insect, but the eggs are resistant. On badly infected 
heads, therefore, the hair cut short. To free the hair of lice 
a good practice is to use equal parts of kerosene and olive oil. Eub 
the mixture well into the scalp, then cover the hair with a piece of 
muslin and fasten it about the head. Care must be exercised to avoid 
a lighted gas jet or flame. In the morning wash the scalp well with 
soap and hot water, then use a flne-toothed comb wet in vinegar to 
remove the nits. Eepeat the treatment two or three nights. 

In the case of the body louse the clothing should be boiled, baked, 
or steamed. Articles injured by heat may be subjected to sulphur 
fumes or dipped in carbolic acid solution. Carbon bisulphid and hydro- 
cyanic acid are also effective. 

For pubic lice white precipitate or mercurial ointment should be 
used and the parts thoroughly washed two or three times a day with 
soft soap and water. 

The principal disease known to be transmitted by lice is typhus 
fever, but it is suspected in relapsing fever and other infections. 


Typhus fever was formerly confused with typhoid fever, but Ger- 
hard in 1829 was the first to insist upon the non-identity of these two 
diseases. Previous to that time typhus fever was the prominent and 
prevailing disease, while typhoid fever was of secondary interest. Now 
the situation is reversed; typhoid fever has become pandemic, while 
typhus fever has receded with civilization and improvements in sani- 
tation. Epidemics of typhus fever are now rare, except in a few 
places, notably the Grand Plateau of Mexico, where the disease prevails 
extensively and with a high mortality. It prevails also in certain por- 
tions of Ireland, in some provinces of France, portions of Russia, 
particularly Poland and the east sea provinces, and at times in Tunis, 
Algiers, and Egypt in JSTorthern Africa; in Spain, Hungary, and cer- 
tain provinces of the Baltic States. 

Typhus fever last prevailed in epidemic form in the United States 
in ISlew York in 1881-82 and again in 1892-93, and in Philadelphia in 
1883, Since then, except for a few sporadic cases at our seaports, the 


disease has been thought to be non-existent in the United States. How- 
ever, Anderson and Goldberger ^ have recently shown that the symp- 
tom-complex known as "Brill's disease" is in reality typhus fever, and 
that the typhus fever of Europe and the typhus fever or "tabardillo" 
of Mexico are the same disease. It is now evident that typhus fever 
has been existent in New York a great many years, certainly since 
1896, when Brill first observed cases of what was known, previous to 
the work of Anderson and Goldberger, as "BrilFs disease.*' The disease 
in New York is generally mild, but seems to be on the increase; there- 
fore, we face a new sanitary problem in this country. 

Typhus fever, when prevalent in epidemic form, has been said by 
the older writers to be one of the most highly contagious of febrile 
diseases, doctors and nurses and others in close contact with the dis- 
ease being almost invariably stricken. The sad case of Ricketts, who 
lost his life in endeavoring to unravel this pathological puzzle in Mex- 
ico, is still fresh in mind. 

The period of incubation of typhus fever is from five to twenty 
days, with an average of twelve. One attack apparently confers a very 
definite immunity, second attacks being very unusual. The cause of 
the infection is unknown. 

Methods of prevention have been given a sound foundation through 
the recent work of Xicolle of France, Eicketts and Wilder of the Uni- 
versity of Chicago, and of Anderson and Goldberger of the U. S. Pub- 
lic Health and Marine Hospital Service. It is now clear that the virus 
exists in the circulating blood during at least all of the febrile stage 
and possibly in some instances for thirty-six hours after the crisis. 

The disease may be transmitted by blood inoculations to chimpan- 
zees and probablv to all the lower monkeys. The virus as it exists in 
the circulating blood is apparently held back by the Berkefeld filter. 
It is not killed by freezing for eight days, but is deprived of virulence 
by heating at 55° C. for 15 minutes. 

Monkeys that recover from the experimental disease show a definite 
immunity to subsequent infection. 

Nicolle in 1909 was the first to report the transmission of typhus 
fever by the bite of the body louse (PediciiJus restimenti). Since 
then his work has been confirmed by Ricketts and Wilder and by An- 
derson and Goldberger. These latter authors have recently shown that 
the head louse (Pedicidits capitis) may also transmit the infection. 
The role of the body louse in the transmission of typhus fever will 
receive ready support from students of the epidemiology' of typhus 
fever, for this disease presents all the characteristics of insect-borne 

^Anderson, John F., and Goldberger, Joseph: "The relation of so-called 
Brill's disease to tvphus fever; an experimental demonstration of their identity." 
Public Health Eeports, XXVII, February 2. 1912. 

LICE 371 

disease. Since the transmission of the disease by the body louse has 
been shown, we can understand why typhus fever prevails in epidemic 
form only in overcrowded, filthy, unhygienic surroundings, and the 
truth is readily understood of the oft-quoted sentence of Hirsch, that 
"the history of typhus is the history of human wretchedness." 

The disease has greatly decreased from civilized centers with dim- 
inution in lousiness. The prevention of typhus now focuses itself upon 
the eradication of the body louse. Fortunately, this insect does not 
of itself travel far, but it may be carried many miles upon the body 
or in the clothing. The eradication of the body louse is largely a 
question of personal cleanliness, and, so far as typhus fever is con- 
cerned, is closely interwoven with squalor, ignorance, and poverty. 

'Now that we know how the disease is spread, measures may be in- 
telligently applied for its prevention, these measures being primarily 
directed to the destruction of the Pediculus vestimenti and its eggs. 
When a case of typhus fever is discovered the patient should be re- 
moved to a vermin-free room or hospital. The patient's clothes should 
be removed and either placed in boiling water or a 1-500 solution of 
bichlorid of mercury for the destruction of lice and their eggs. The 
patient's hair should be clipped and he should then be given a thor- 
ough sponging with a 1-2,000 solution of bichlorid of mercury for the 
destruction of lice eggs. The room or apartment from which the pa- 
tient was removed should be thoroughly fumigated by the burning of 
sulphur for the destruction of lice, and the room kept sealed for at 
least 12 hours. 

The fact should be kept constantly in mind that the louse is neces- 
sary for the spread of typhus fever, just as the mosquito is for the 
spread of malaria, and our efforts toward prophylaxis should be con- 
ducted with this point continuously in mind. Even with the knowledge 
of the mode of transmission of typhus fever individual prophylaxis is 
still somewhat difficult, especially where infected insects abound in 
thickly populated centers. 

Those whose duties — such as doctors and nurses — take them into 
an infected area should avoid outer clothing which is liable to brush 
against the furniture, bedding, etc. The skirts of nurses should be 
sufficiently short to avoid touching the floor; trousers should be rolled 
above the shoe-tops and the sleeves above the elbows, so that occasional 
vermin which may lodge on the hand may be more readily detected. 
Eucalyptus oil has been recommended for smearing the neck, wrists, 
and ankles. Personal prophylaxis may also be assisted through the 
use of gloves, veils, netting, and similar mechanical devices. The cloth- 
ing worn by those attending cases of the disease where lice are present 
should be frequently changed and close attention given to personal 




Cimex leciularius has been carried by man to all parts of the in- 
habited world. It has become a true domesticated animal and has 
accommodated itself well to the environment of human habitations. 
The bedbug lias no wings and a very flat body, which enables it to hide 
in tlie narrowest chinks and cracks of beds and wells. It may subsist 
for incredibly long periods of time without food. It is nocturnal in 
its habits. 

The pronounced odor of this insect is produced by certain glands 
opening on the back of the abdomen in young bugs and on the under 

Fig. 46. — The Bedbug. 

a, Adult female, gorged with blood; b. Same from below; c, Rudimentary wing pad; 

d, Mouth parts. (Marlatt.) 

side of the metasternum in the adults. The odor is common to most 
members of the group to which this insect belongs. It is useful in 
plant bugs, protecting them from their enemies. 

The bedbug undergoes an incomplete metamorphosis, the young be- 
ing very similar to their parents in appearance, structure, and habits. 
The eggs are white, oval objects having a little projecting rim around 
one edge, and are laid in batches of from six to fifty, in cracks and 
crevices where the bugs go for concealment. The eggs hatch in a 
week or ten days and the young escape by pushing the lid within the 
projecting rim from the shell. At first the larvae are yellowish-white, 
nearly transparent, the brown color of the more mature insect increas- 
ing with the later molts. During the course of development the skin 
is shed five times, and with the last molt the minute wing pads, char- 
acteristic of the adult insect, make their appearance. Marlatt found 
that under favorable conditions about seven weeks elapse from the egg 


to the adult insect, and that the time between each molt averages about 
eight days. Without food they may remain unchanged for an indefinite 
time. Ordinarily but one meal is taken between molts, so that each 
bedbug must puncture its host five times before becoming mature, and 
at least once afterward before it can develop eggs. 

The presence of bedbugs in a house is not necessarily an indication 
of neglect or carelessness. They are very apt to get into trunks and 
satchels of travelers or may be introduced in the homes upon the cloth- 
ing of servants, workmen, or visitors. The bedbug is quite capable of 
migrating from one house to another. Ships are almost sure to be 
infested with them. They are not specially limited by cold, and are 
known to occur well north. They thrive particularly in old houses 
which are full of cracks and crevices, in which they can conceal them- 
selves beyond easy reach. The biting organ of the bedbug is similar 
to that of other Hemipterous insects. The skin of the host or victim 
is pierced with four thread-like hard filaments or setae, which glide 
over each other with an alternating motion and thus pierce the skin. 
The blood is drawn up through the beak, which is closely applied to 
the point of puncture. The bite of the bedbug is decidedly poisonous 
to some individuals, resulting in a swelling and disagreeable inflamma- 

The Suppression of Bedbugs. — On account of its habits of conceal- 
ment the bedbug is usually beyond the reach of the ordinary insect 
powders, which are practically of no avail against it. If iron or brass 
bedsteads are used, the eradication of the insect is made easier. Large 
wooden bedsteads furnish many cracks and crevices into which the bugs 
can force their flat thin bodies, and extermination becomes a matter 
of considerable difficulty. The most practical way of eradicating bed- 
bugs is by a very liberal application of gasolene, benzine, kerosene, or 
any other of the petroleum oils. These must be introduced into all 
crevices with small brushes or feathers, or by injecting with small 
syringes; a saturated solution of corrosive sublimate in water is also 
of value, and oil of turpentine may be used in the same way. The 
liberal use of scalding hot water or soap suds wherever it may be em- 
ployed without damage to furniture is also an effectual method of, de- 
stroying both eggs and active bugs. Fumigation with hydrocyanic acid 
gas, sulphur dioxid, or carbon bisulphid are alike effective. Crevices in 
warm parts of the room are favorite nesting places, as under picture 
mouldings, or over door frames. 

In sleeping cars and other places where hydrocyanic acid gas may 
be used without fear of accidents, this is the most efficacious and least 
destructive method. 

The bedbug has long been under suspicion as an intermediate host 
in the transference of manv communicable infections. There is more 


than a suspicion that it is concerned in relapsing fever, in kala-azar, 
and it has been accused of carrying the bacteria of tuberculosis, leprosy, 
and many other diseases. 


Kala-azar is a tropical infection characterized by anemia and en- 
largement of the spleen. It is caused by a parasite which occurs in 
great numbers in the spleen and which, upon culture media, develops 
into a flagellated organism resembling the trypanosomes.. The trypano- 
somes w^ere discovered by Leishman and Donovan in the spleen and 
liver and the epithelium of the blood vessels. Manson and Low found 
similar bodies in the ulcerous mucous membranes of the intestines, and 
Marchand and Ledingham found the same peculiar bodies in the cells 
of the bone marrow^ and lymphatic glands. Rogers cultivated the para- 
sites from the spleen of patients suffering with kala-azar upon agar 
streaked with fresh human blood. Flagellate forms developed. This 
was confirmed by Christophers, who used Xovy's method of growing 
trypanosomes upon the water of condensation of blood agar tubes. 
The kala-azar parasites grow'n in artificial culture media liave a cilium 
but no membrane. 

References. — The literature upon insects and insect-borne diseases 
is very widely distributed. Many of the entomological facts contained 
in this chapter have been taken from "The Insect Book" by L. 0. 
Howard and the many excellent publications of Howard and his col- 
leagues of the Bureau of Entomology, Department of Agriculture. 
The Government publications may be had upon application to the Su- 
perintendent of Documents, Washington, D. C. Many of the facts 
concerning the prevention and destruction of mosquitoes have been 
taken from articles in the Public Health Reports of the Public Health 
and Marine Hospital Service. In the chapter upon insecticides free 
reference has been made to my own book upon "Disinfection and Dis- 
infectants," as well as my other writings and unpublished work in 
different phases of this subject. 




(Acute Anterior Poliomyelitis) 

An entirely new literature upon the subject of infantile paralysia 
is now being constructed. The chief contributors to this recent advance 
in our knowledge have been Wickman of Sweden, who, in 1905-06, gave 
us a new symptomatology, and defined clinical types not before recog- 
nized. Wickman made the first systematic study of the disease from 
an epidemiological point of view, and found evidence that it was con- 
tagious, though usually slightly so. He directed especial attention 
to several factors in its spread, viz. : routes of travel, public gath- 
erings of children, abortive or ambulant cases, and healthy inter- 
mediate carriers. In the spring of 1909 Landsteiner and Popper 
succeeded in transmitting the disease to two monkeys by inoculating 
them with the spinal cord of a child who had died of infantile paral}^- 
sis. Later in the year Flexner and Lewis obtained the same results, 
and further transmitted the infection from monkey to monkey through 
an indefinite number of passages. To Harwitz and Scheele of Nor- 
way we are indebted for formulating the pathologic anatomy of the 

Infantile paralysis is now properly regarded as a communicable dis- 
ease. The virus is filterable, that is, "ultramicroscopic,^' yet coccae 
forms have been described by jSToguchi and Flexner in artificial cultures. 
(J. A. M. A., Feb. 1, 1913, LX, 5, 362.) 

It appears that infantile paralysis is becoming more and more com- 
mon and more widespread of late years. This increase cannot be ac- 
counted for by the fact that the disease is now better known and more 
readily recognized. Bergenholtz, in 1881, described the first out- 
break with sufficient accuracy to accept infantile paralysis as a new 
disease. Since that time the number of outbreaks and the number of 
cases have progressively increased, as shown in the following table : 



Av. Xo. of Cases 

Cases Outbreaks per Outbreak 

1880-1884 23 2 11.5 

1885-1889 93 7 13. 

1890-189-i 151 4 38. 

1895-1899 345 23 15. 

1900-1904 349 9 39. 

1905-1909 8,054 25 322. 

Eecent outbreaks bave occurred in Xorway and Sweden, Austria, 
Germany. Holland. England, Spain, France, the United States, and 
Cuba. Of the 8,054 cases reported in 5 years (1905-09), the United 
States contributed 5,514 cases or about five-sevenths of the total number. 

Epidemics of poliomyelitis have prevailed in all quarters of the 
world. The disease has been most prevalent in the northern parts of 
Europe and of the United States. Epidemics have been more severe, 
and the case rates have been higher, in small towns and rural dis- 
tricts than in the more densely populated cities. Even in the cities 
the disease does not especially strike the crowded districts. Cold coun- 
tries having marked seasonal variations in temperature have been most 
affected, but the disease is always most prevalent in the warm, dry 
months, from May to Xovember in the northern hemisphere and Xo- 
vember to May in the southern hemisphere. Sporadic cases may occur 
at any time throughout the year. The great majority of cases occur in 
children under five years of age. From the standpoint of prevention it 
is important to note that social and hygienic conditions apparently have 
no influence whatever in determining the infection. All classes are 
affected in about equal proportion. 

The virus of the disease is present in greatest virulence or concen- 
tration in the spinal cord of infected persons and animals. One one- 
hundredth of a cubic centimeter of an emulsion of cord, or less, is suf- 
ficient to infect a monkey. The virus is also quite constantly present 
in the brain and other organs and tissues, as, for instance, the mucous 
membrane of the nose and pharynx, the mesenteric glands, the axillary 
and inguinal lymph nodes, also in the blood, and in the cerebrospinal 
fluid. The virus has been demonstrated in the feces. The suspicion 
that the alvine discharges may, therefore, be virulent is sufficient indica- 
tion that they should be disinfected in all cases until further knowledge 
of the subject is at hand. 

The experimental disease in monkeys may be produced with cer- 
tainty by injecting the virus directly into the central nervous system, 
preferably the brain. Monkeys may also be infected by introducing 
the virus subcutaneously or into the peritoneal cavity, and even by in- 
travenous inoculation. They have been infected by placing virulent 


material upon the healthy mucous membrane of the nose and also by 
inhalation of the infectious material forced into the trachea, and finally 
by introducing the virus into the stomach, along with an opiate, to re- 
strain peristalsis. Leiner and Weisner have infected monkeys through 
the uninjured nasal mucous membrane. This, however, is an uncertain 
method of inoculation. ]\Ionkeys have so far never been known to con- 
tract the disease spontaneously, even though they are kept in intimate 
association with infected monkeys. There are many similar paralytic 
diseases of the lower animals, but. so far as known, infantile paralysis 
as a natural infection is peculiar to man. Recently Eosenau and Brues, 
and also Anderson and Frost, have transmitted the disease from monkey 
to monkey through the bite of the stable fly. 

Resistance of the Vims. — The virus of anterior poliomyelitis is 
killed by a temperature of 45° to 50° C. in half an hour; also by com- 
paratively weak disinfectants, such as a 1-500 solution of permanganate 
of potash, 1 per cent, menthol in oil, a powder containing menthol, 0.5 
per cent., salol, 5 per cent., boric acid, 20 per cent. (Landsteiner and 
Levaditi), and a dilution of perhydrol (Merck) equivalent to 1 per 
cent; of peroxid of hydrogen. The virus is not destroyed by very low 
temperatures nor by drying over caustic potash, or in vacuo for a con- 
siderable period. A virulent cord has been kept for almost 5 months in 
pure glycerin without losing its virulence, resembling in this respect 
rabies, vaccine, and other filterable viruses, and differing for the most 
part from non-spore-bearing pathogenic bacteria which are usually 
killed by pure glycerin in a short while. 

Immunity. — One attack of infantile paralysis apparently confers a 
high degree of immunity. Recurrent cases and second attacks have 
been reported. Monkeys which have recovered from the infection show 
a high degree of resistance, in that they are not susceptible to infec- 
tion by again inoculating them, and their blood serum contains anti- 
bodies capable of rendering the virus harmless. That is, if the blood 
serum of an immune monkey is mixed with an emulsion of virulent 
spinal cord and the mixture allowed to stand for several hours, the 
virus is no longer capable of producing the infection in susceptible 
animals. This property has been used by Anderson and Frost to cor- 
roborate the clinical diagnosis in abortive cases. The blood of a per- 
son who has not had the disease does not neutralize the virus; there- 
fore, if the injection of the virus previously treated with human serum 
fails to produce the infection in susceptible monkeys, it may be taken 
as evidence that the serum contained specific antibodies and came from 
an individual who has had the disease. 

Modes of Transmission. — Coxtact theory (based upox the as- 


AND ENTERS THROUGH THE SAME chaxnel). — There is evidence to sup- 


port the theory that the disease is directly transmissible from person to 
person and there is a suspicion that healthy carriers play an important 
role in spreading the infection. This view was enunciated by Wickman 
and received support through the experiments of Kling, Pettersson and 
Wernstedt, and also Flexner. It is known that the mucous membrane 
of the nose and throat contains the virus, and in one case the salivary 
glands were shown to be infective. Osgood and Lucas demonstrated 
that the nasal mucous membrane of two monkeys experimentally inocu- 
lated with poliomyelitis remained infective for 6 weeks in one case and 
51/2 months in another. This very important observation strengthens 
the suspicion of the existence of chronic human carriers. If healthy 
carriers continue to spread the infection months after the attack, it in- 
creases the difficulty of suppressing the disease, and further renders 
doubtful the efficiency of strict isolation and prophylactic measures di- 
rected only to persons in the acute stage of the disease. The fact that 
the mucous membrane contains the virus is not, however, sufficient proof 
that the virus is liberated and discharged in sufficient amount in the 
secretions from the mouth and nose to be a menace. In a series of 18 
cases Eosenau, Sheppard and Amoss ^ were unable to demonstrate the 
virus in the nasal and buccal secretions obtained from persons in various 
stages of convalescence. Strauss ^ had similar negative results in a series 
of 10 cases. On the other hand, Kling, Pettersson and Wernstedt ^ re- 
port successful results ; by experiments upon monkeys they demonstrated 
the infectiousness of buccal and intestinal secretions of living subjects. 
Flexner has recently also reported one successful attempt in demonstrat- 
ing the virus in the buccal secretions. 

The Insect-borne Theory. — Infantile paralysis shows no tendency 
to prevail in congested centers or to spread in hospitals, schools, institu- 
tions, and other crowded places; its seasonal prevalence corresponds to 
the seasonal prevalence of most insects, and does not correspond to the 
seasonal prevalence of diseases spread through secretions of the mouth 
and nose, such as diphtheria, scarlet fever, smallpox, etc. ]\Iany other 
factors, brought to light by the studies of the State Board of Health of 
Massachusetts upon the epidemiology of the disease, under the able 
direction of Dr. Mark Eichardson, indicate that the disease is not a 
contagious one. These studies * gradually focused attention upon some 

' Eosenau, M. J., Sheppard, P. A. E.. Amoss, H. L., Boston Med. and Surg. 
Jour., May 25, 1911, CLXIV, 21, pp. 743-748. 

^Strauss, I., J. A. M. A., April 22, 1911, LVI, 16, 1192. 

* Kling, C., Pettersson, A., and Wernstedt, W., Eeport from the State Medical 
Institute of Sweden to the XV Internationa] Congress on Hygiene and Demog- 
raphy, Washington, D. C, 1912. Also, Zeitschr. f. Immunitdtsforch. u. exper. 
Therapie, Bd. XII, Jena, 1912. 

* Richardson, M. W., Monthly Bull, State Board of Health of Mass., Sept., 
1912, 7, 9, pp. 308-315. 

Lovett, R. W., Report to the Mass. State Board of Health, 1907. 
Report to the Mass. State Board of Health, 1908, 1909, 1910, 1911. 


insect, the stable fly (Stomoxys calcitrans) in particular. Eosenau and 
Brues ^ demonstrated that the virus may be transmitted from monkey 
to monkey through the bite of the stable fly. These results were soon 
confirmed by Anderson and Frost.- The insect-borne theory seems to 
fit the case as the disease is known in Massachusetts. It will, however, 
require much additional study to determine what role Stomoxys cal- 
citrans plays in spreading the infection in nature. 

Other Theoeies. — It has been suggested that the virus may be 
air-borne in the sense that it is carried in the dust. Neustaedter and 
Thro ^ have infected monkeys from dust collected from sick rooms. In- 
fected food, or transmission through wounds and other means, have not 
been ruled out of consideration. 

Prevention. — No definite or effective system of prevention can be 
formulated until we are sure of the mode of transmission. Meanwhile 
health authorities are entirely justified in requiring cases to be reported, 
isolated, and all known lines of preventive measures applied, such as 
disinfection, screening, and guarding against insects, allaying unneces- 
sary dust, etc. A fly campaign directed with especial reference to the 
stable fly is plainly indicated, and the infection must also be fought as 
one conveyed from man to man directly. Until the modes of transmis- 
sion of the disease are established, however, we can have no confidence 
in our prophylactic measures, which most resemble the old "shotgun" 

The following measures are recommended: The patient should be 
isolated as completely as possible in a clean, bare room, well screened 
to keep out insects. This is a good practice despite the fact that the 
disease shows no tendency to spread in children's asylums, hospitals, 
and other institutions, or even in the home. The same statement, 
however, was made of typhoid fever not many years ago. Visiting 
should be interdicted and only the necessary attendant should be al- 
lowed to come in contact with the patient. All discharges, including 
sputum, nasal secretions, urine, and feces, should be thoroughly disin- 
fected, and special care should be taken that cups, spoons, remnants of 
food, etc., which may have become contaminated by the patient are 
burned, scalded, or otherwise purified. 

Towels, bed linen, and other fabrics should be boiled or dipped 
into a germicidal solution strong enough to destroy the typhoid bacil- 
lus. The nurse and physician should observe the same precautions re- 

^ Eosenau, M. J., and Brues, C. T., Monthly Bull, State Board of Health of 
Mass., Sept., 1912, 7, 9, pp. 314-318. Also Brues and Sheppard, Jour, of Econom. 
Entomology, Aug., 1912,^ V, 4, 305. 

-Anderson, J. F., and Frost, W. H., Puh. Health Reports, Oct. 25, 1912, 
XXVII, 43, pp. 1733-1736. 

^Neustaedter, M., and Thro, W. C, N. Y. Med. Jour., Sept. 23, 1911, 
XCIV, 13. 


garding their hands and clothing as are recommended in attending a 
case of scarlet fever. 

The period during which tlie isolation should l)e maintained can- 
not even be guessed at. Children are usually not permitted to return 
to school for at least three weeks, but, if chronic carriers play the im- 
portant role now suspected, this time would be far too short in many 

Since the virus can be killed experimentally by a 1 per cent, solu- 
tion of jicroxid of hydrogen, antiseptic gargles, sprays, and nose washes 
of this solution are recommended to be used by the patient, the nurse, 
and physician, and other members of the family. In the presence of 
an epidemic, street and house dust should be kept down by sprinkling, 
oiling, and the other means employed for this purpose. Dust should 
be allayed whether there is an epidemic of infantile paralysis or not. 
During epidemics children should be kept away from public gather- 
ings, prohibited from using public drinking cups, and special attention 
given to the diet to prevent gastrointestinal disorders, for many a case 
of infantile paralysis starts with a digestive upset. 


Chickenpox is one of the minor communicable diseases, in that the 
mortality is practically nil and that complications and sequela} are rare. 
Chickenpox is very readily communicable and spreads through families 
or institutions, but does not occur in widespread epidemics. The cause 
of the disease and its modes of transmission are not known. The virus 
is not contained in the content of the vesicle. Tyzzer and others made 
numerous inoculations with both clear and clouded vesicle contents 
without results. The disease is probably peculiar to man; animal 
inoculations have so far proven negative. The period of incubation is 
probably from fourteen to sixteen days, and one attack p^'oduces a defi- 
nite immunity. No age is exempt. 

The differential diagnosis between chickenpox and smallpox is often 
an important and difficult public health matter. The distinction may 
be made by introducing some of the contents of the vesicle into the skin 
of a well-vaccinated person. If chickenpox, an immediate reaction 
results; if smallpox, no reaction results. Monkeys are not susceptil)le 
to chickenpox but may be given smallpox. The differential diagnosis 
may also be made from the presence of vaccine bodies in smallpox and 
their absence in chickenpox. These bodies are best demonstrated by 
introducing some of the virus upon the cornea of a rabbit, and examining 
the vesicles which form. 

Health officers should require cases of chickenpox to be reported, 
if for no other reason than that it is often mistaken for smallpox. The 


differential diagnosis may be made in doubtful cases by a histological 
examination of the pock, or by inoculating the contents of the vesicle 
upon the cornea of rabbits. In sections of the skin lesion the vaccine 
bodies are found in smallpox, not in chickenpox; the vesicle of the 
former is multilocular, the latter unilocular. The vesicle upon the 
cornea of rabbits produced by smallpox is distinct and contains the 
vaccine bodies; the lesion resulting from chickenpox is trifling and 
does not contain the vaccine bodies. 

The prevention of chickenpox depends upon isolation and disinfec- 
tion at the bedside. Children with chickenpox should not be permitted 
to go to school. 


Glanders or farcy is a widespread communicable disease of horses, 
mules, asses, and other animals, and is readily communicated to man. 
In both man and horses it is remarkable for its fatality. The disease 
is characterized by the formation of inflammatory nodules either in 
the mucous membrane of the nose (glanders) or in the skin (farcy). 

Glanders is caused by the Bacillus mallei, which corresponds to 
the spore-free bacteria so far as its resistance is concerned. In gen- 
eral the bacillus of glanders is killed by the same agents used against 
the tubercle bacillus, which it resembles in some particulars. 

The infection may be introduced into the system either through the 
skin or mucous membrane, and is usually communicated directly from 
the horse to man by contact with the infected discharges. The disease 
is sometimes communicated from man to man. Washerwomen have 
become infected from the clothes of a patient. 

The bacillus of glanders does not have a spore. It is comparatively 
frail and readily destroyed by the usual physical and chemical germi- 
cidal agencies used against spore-free bacteria. The bacillus, however, 
is frequently protected by albuminous matter or buried in the dirt of 
stables, water troughs, harnesses, and other objects. While the naked 
germs of glanders are readily destroyed, they are frequently hard to 
get at; cleanliness is, therefore, imperative. 

The prevention of glanders in man depends primarily upon the 
suppression of the disease in horses. The only difficulty in controlling 
the disease in horses lies in the early diagnosis and recognition of 
mild or missed cases, which are very common. Horses affected with 
occult or latent glanders are important factors in the propagation of 
the infection. The clinical diagnosis in the frank cases is made with- 
out difficulty from the characteristic symptoms and the lesions, but 
laboratory aid is necessary to discover the mild cases. 

Diagnosis. — The diagnosis of glanders may be made by: (1) the 
mallein test; (2) the agglutination test; (3) the Strauss reaction; 


(4) isolation of B. mallei in pure culture; and (5) complement fixa- 
tion. All these tests serve a definite purpose. However, the mallein 
test, the agglutination test, and the Strauss reaction are not sufficiently 
reliable to be entirely satisfactory. The isolation of the glanders bacil- 
lus in pure culture is definite and final, but time-consuming. The 
diagnosis of glanders by complement fixation is at present our most 
reliable, most satisfactory, and quickest method of recognizing the 

The Mallein Test. — ^lallein is a product of the glanders bacillus 
corresponding to tuberculin. The injection of mallein into normal ani- 
mals produces no reaction, whereas the injection into glanderous ani- 
mals causes a rise in temperature and a local reaction about the le- 
sions. With the mallein test a large proportion of latent and occult 
cases of glanders can be diagnosed, but the test must be made and in- 
terpreted by an experienced veterinarian, else the results may be un- 
reliable. The mallein test fails to give a typical reaction in a consid- 
erable number of glanderous animals; on the other hand, a reaction 
may follow the injection of mallein in the absence of glanders. Thus 
mallein is not an entirely reliable diagnostic agent and has never been 
considered as specific in the detection of this disease as tuberculin 
for the diagnosis of tuberculosis. 

The Agglutination Test. — The agglutination test is of value in 
all cases of recent infection, the blood serum possessing a very high 
agglutinating power — 1-1,000 and higher. In chronic glanders the 
agglutinating power of the blood may be very low — 1-400 or less; in 
some cases even lower than that of normal blood serum — which may be 
1-800 and even higher. It is, therefore, plain that agglutination tests 
alone do not constitute an entirely satisfactory diagnostic method for 
glanders. It may be used as an adjunct to other tests. 

The Strauss Reaction. — The Strauss ^ reaction for the diagnosis 
of glanders consists in inoculating male guinea pigs into the peritoneal 
cavity with material containing virulent B. mallei, which causes an 
enlargement of the testicles. A positive reaction associated with organ- 
isms resembling those of glanders, and typical cultures obtained from 
the lesions, are unfailing evidence of the presence of the specific virus. 
Failure to obtain the reaction is not proof that a suspected specimen 
may not have come from a horse or animal with glanders. Arms ^ 
recommends that it is better to use more than one guinea pig in test- 
ing suspected material, and that, before inoculating, it is well to 
make a microscopic examination as a guide to the dosage. A cul- 
ture made from the swab often aids in the early diagnosis. Gui- 
nea pigs should be kept under observation for a month, and if a 

' Compt. Bend. Acad. d. Sc, 1889, CVIII, p. 530. 
V. A. M. A., LV, 7, Aug. 13, 1910, p. 591. 


lesion of any kind is present an autopsy should be made and cultures 

The Isolation of B. Mallei in Pure Culture. — The bacillus 
of glanders may be isolated by introducing some of the suspected ma- 
terial subcutaneously and also intraperitoneally into male guinea pigs. 
In this way pure cultures may be obtained from the pus or necrotic 
foci in the spleen, which follow subcutaneous inoculation; or from the 
characteristic enlargement of the testicle which is observed in animals 
inoculated intraperitoneally. The organism isolated must be studied 
for cultural, morphological, and biological characters. The isolation of 
the bacillus in pure culture gives positive information of unquestioned 
character in any critical case. The method is not generally applicable 
to the diagnosis of glanders because it requires too much time and 
may occasionally fail to discover the bacillus. 

Complement Fixation. — In 1909 Schiitz and Schubert ^ published 
the results of their important work on the application of the method 
of complement fixation for the diagnosis of glanders. The splendid 
results obtained constitute, without doubt, the most reliable method 
for the diagnosis of glanders which we have at our command at the 
present time. The complement fixation test is, in fact, one of the most 
specific of the biological tests in immunity. It is readily applicable to 
the case of glanders. The essential elements used in the test are as 
follows : 

The hemolytic system consists of the washed red blood corpuscles 
of a sheep and the blood serum of a rabbit which has been injected 
with the washed red blood corpuscles of a sheep. Strong, vigorous 
rabbits are selected and three injections of the sheep's corpuscles are 
made at intervals of 7 days, using 7 c. c, 10 c. c, and 12 c. c. of the 
red corpuscles of the sheep suspended in like amounts of isotonic salt 
solution. The blood serum of a rabbit so treated contains the hemolytic 
amboceptors. The rabbit's blood serum is heated to 56° C. for half 
an hour in order to destroy the complement. The titer, or amount of 
amboceptor contained in the rabbit serum, must be determined. The 
hemolytic system, then, consists of rabbit serum containing ambocep- 
tor, plus washed red blood corpuscles of the sheep. 

Complement. — The complement is contained in the fresh blood 
serum of a healthy guinea pig. The blood serum of the guinea pig 
should be titrated in order to determine the amount of complement 
present. It is always necessary to determine the smallest quantity of 
complement to be used for the final test. 

Antigen. — The antigen consists in an extract obtained by shaking 

^ Schiitz and Schubert : ' ' Die Ermittelung der Eotzkrankheit mit Hilf e der 
Komplementablenkungsmethode. ' ' Archiv fur wissenschaftliche und praktische 
Tierheilkunde. Bd. 35, Heft 1 and 2, pp. 44-83, 1909. 


glanders bacilli in salt solution. The bacillus is grown in pure cul- 
ture on 2 per cent, acid glycerin agar. A luxuriant growth upon the 
surface of the medium is usually obtained in 48 hours. This is sus- 
pended in salt solution, heated to 60° C. for four hours in order to 
kill the bacilli. After heating the dead bacilli are shaken in the salt 
solution in a special apparatus for four days. The bacilli are separated 
in the centrifuge and the clear supernatant liquid is drawn off and pre- 
served with carbolic acid. The strength of this extract must be deter- 
mined by suitable methods of titration. 

Technique. — The test is carried out by adding together, in proper 
proportions, the following: (1) The blood serum of the horse to be 
tested; (2) the antigen (extract of glanders bacilli); (3) complement 
(fresh guinea pig serum) ; and (4) the hemolytic system. If the blood 
serum of the horse to be tested contains the specific amboceptors these 
will unite with the bacteria, fix the complement, and thus prevent 
hemolysis. If the blood serum of the horse to be tested does not con- 
tain these specific amboceptors, this fixation of the complement cannot 
take place and hemolysis results. Therefore, the absence of hemolysis 
means the presence of glanders, and vice versa. The tests must always 
be carried out with controls and carefully conducted as to the amount 
of each substance used, the temperature and time.^ 

Prevention. — T\Tien glanders is discovered or suspected among horses 
in a stable, the blood of all the horses in the infected stable should be 
drawn and tested in the manner above described. All animals whose 
serum shows complement fixation should be destroyed without further 
consideration. After the animals have been killed and properly dis- 
posed of, the stable should be thoroughly cleansed and disinfected. All 
other horses which have in any way been associated with the infected 
animals should be carefully watched and tested again after three weeks, 
and, should there be no indication of the disease in the second test, 
the stable may be considered free from the infection; otherwise the 
infected animals should be destroyed and the tests repeated every three 
weeks until the disease has been eliminated. 

The eradication of glanders from a stable often means considerable 
loss and sometimes a sacrifice of valuable animals, but it is only through 
vigorous measures that the disease may be controlled. In the disin- 
fection and cleansing special attention should be paid to the stalls, 
harnesses, water troughs, bits, food containers, curry combs, sponges, 
and other objects exposed to the infection, which is eliminated mostly 
in the secretions from the mouth and nose. The common drinking trough 
for horses spreads the infection. 

' A complete description of the diagnosis of glanders by complement fixation, 
giving in full all the details, will be found in Bull. 136, Bureau of Animal 
Industry, Apr. 7, 1911, by Mohler and Eichhorn. 


The personal prophylaxis of glanders in man depends upon the 
education and care of those who have to handle horses. In working 
with horses known to be infected rubber gloves, disinfection, and other 
methods of protection should be employed. Special care should be 
taken to prevent the spread of the infection through the discharges or 
by infected fomites from human cases. Fatal accidents have occurred 
in laboratories in research workers handling pure cultures of B. mallei. 


Anthrax belongs to that group of diseases which occurs primarily 
in the lower animals and secondarily in man. The infection is found 
in horses, cattle, sheep, and other cloven-hoofed animals, and may be 
transmitted experimentally to mice, guinea pigs, rats, and rabbits. 
Cold-blooded animals and birds, as well as dogs and swine, are re- 

In man the infection may enter the skin (malignant pustule) or 
may enter the lungs (wool sorters' disease), or may enter the diges- 
tive tract and produce intestinal lesions. In anthrax of the skin the 
infection usually enters through slight abrasions, scratches, or small 
wounds, especially on the forearm, hand, or face. Most of the cases 
occur in butchers or persons who have to handle infected carcasses. 
The spores have been carried to the skin by flies and may be inoculated 
by the bite of the stable fly. 

Wool sorters' disease, or anthrax of the lungs, appears to be due 
to the inhalation of anthrax spores. It is observed only among per- 
sons who handle skins or who work with horse hair or other raw materials 
from animals afflicted with anthrax. 

The mode of transmission in intestinal anthrax is through meat 
from an anthrax cadaver which is partaken of without proper cooking. 

Schuberg and Kuhn ^ have shown that anthrax may be transferred 
from animal to animal through the bite of the stable fly (Stomoxys 

Resistance. — The anthrax spore is exceedingly resistant to heat and 
external influences, such as dryness and sunlight, and also to germi- 
cidal agents. Its resistance may be compared to the tetanus spore 
page 70. 

Immunity. — A number of species of animals have a natural immu- 
nity to anthrax, and an artificially acquired immunity may be induced 
in cattle or sheep through the injection of attenuated cultures, in ac- 
cordance with the classical method of Pasteur. These procedures are 
not applicable to man. The prevention of the disease in man must 
first be directed to a suppression of the disease in animals. The sick 

'Arbeiten a. d. kajserl. Ges.-Amt., Bd. XL, Heft 2, 1912. 


animals should be isolated, or, better, killed, and the carcasses burned 
or buried at least three feet deep. The carcasses may be ""tanked," 
that is, subjected to a prolonged exposure to steam under pressure. 
Tanks for tliis purpose are found in all the larger slaughter houses. 
It is important in handling the body of an animal dead of anthrax 
not to open it or shed blood, for the bacillus does not produce its spore 
except in the presence of oxygen, that is, the bacilli are mainly in the 
blood and internal organs and will not sporulate as long as access to the 
air is prevented. 

Prevention. — The chief preventive measure so far as man is con- 
cerned is the disinfection of all raw material in those trades in wliich 
horse hair, hides, and other substances liable to harbor the anthrax spore 
are handled. Veterinary surgeons who conduct autopsies upon anthrax 
animals should exercise unusual precautions, and, if practicable, wear 
rubber gloves. 

Ponder ^ recommends the following process to destroy anthrax in- 
fection in hides: The dry hides are placed for 24 hours in a "soak" 
which is made to contain 1 to 2 per cent, of formic acid and 0.02 per 
cent, of bichlorid of mercury, and then salting them with sodium 
chlorid. The action of the "soak" is to swell up the fibers of the hide 
by causing them to absorb water, the result being that the hide returns 
to a condition closely resembling that in which it was taken from 
the animal's carcass. This permits the bichlorid of mercury to per- 
meate and exert its germicidal action. 


Foot-and-mouth disease is also known as aphthous fever, epizootic 
catarrh, and eczema contagiosa. It is an acute and highly commu- 
nicable disease, generally confined to cloven-footed animals, and char- 
acterized by an eruption of vesicles on the mucous membrane of the 
mouth and on the skin between the toes and above the hoofs. The 
vesicles rupture, forming erosions and ulcers. There are also saliva- 
tion, tenderness of the affected parts, loss of appetite, lameness, emacia- 
tion, and diminution in the quantity of milk secreted. 

Foot-and-mouth disease is primarily a disease of cattle and sec- 
ondarily of man. Hogs, sheep, goats, buffalo, American bison, camel, 
chamois, llama, giraffe, antelope, and even horses, dogs, and cats may 
occasionally become infected. 

The disease prevails in European countries and occasions great 
economic loss. The mortality is low ; the serious losses depend chiefly 
upon the diminution of the milk secretion and the loss of flesh in the 
affected animals. 

^Lancet, London, Nov. 4, CLXXXI, No. 4601, pp. 1247-1314. 


Foot-and-mouth disease has appeared in the United States only on 
five different occasions— in 1870, 1880, 1884, 1902-3, and 1908. Every 
outbreak on American soil has thus far been foUovred by its complete 
suppression through the application of well-known preventive meas- 
ures, such as isolation, destruction and burial, of the affected herds, 
disinfection, and a systematic inspection of all farms in the infected 
area to detect cases of the disease. 

Loffler and Froesch in 1898 showed that the virus will pass the 
finest porcelain filters. This was the first ultramicroscopic virus dis- 
covered. The specific principle is contained in the serum of the ves- 
icles; in the saliva, milk, and various other secretions and excretions; 
also in the blood during the rise of temperature. 

No definite immunity is rendered by an attack. The period of in- 
cubation is variable, usually from two to six days or longer, excep- 
tional instances being prolonged to fifteen or even eighteen days. 

The disease in man is a direct counterpart of that in cattle. The 
infection is transmitted to man through the ingestion of raw milk, 
buttermilk, butter, cheese, and whey from animals suffering with foot- 
and-mouth disease. It may also, though more rarely, be transmitted 
directly from the salivary secretions or other infected material which 
gains entrance through the mucous membrane of the mouth. It is 
doubtful whether the disease can be transmitted to man by cutaneous 
or subcutaneous inoculation, though it is probable that the infection 
may be communicated if the virus enters the blood directly through 
wounds of any kind. Children are most frequently infected by drink- 
ing unboiled milk during the time in which the disease is prevalent 
in the neighborhood, while persons in charge of diseased animals may 
become infected through contact with the affected parts or by milking, 
slaughtering, or caring for the animals. The disease is usually very 
mild in man; death practically never results, except in weakened chil- 
dren, and then from secondary complications. 

The original experiments of Loffler and Froesch, as well as recent 
experiments which have been made in Denmark and Germany, indicate 
that the infection is destroyed comparatively readily by heat or the 
usual antiseptics. Milk pasteurized at a temperature of 60° C. for 
20 minutes is safe, so far as infection from foot-and-mouth disease is 

Foot-and-mouth disease has a special interest on account of the 
fact that it may be associated with vaccinia. The symbiosis between 
the infections of vaccinia and foot-and-mouth disease is remarkable. 
Animals vaccinated with the mixed virus, as a rule, show the lesions 
of only one of these diseases, namely, vaccinia. Nevertheless, the in- 
fectious principle of the other, foot-and-mouth disease, remains in the 
vaccinal eruption. Vaccine virus has been known to contain the in- 


fectjon of foot-and-mouth disease.^ Glycerin acts as a preservative 
for the virus of foot-and-mouth disease, so that it may remain viable 
in fflycerinated vaccine virus a very long time. No instance of the 
transmission of foot-and-mouth disease to man through vaccine virus 
has been recorded, and it is doubtful, in view of the known facts, 
whether it is possible to reproduce the disease in man by the cutaneous 
inoculation commonly used in the process of vaccination. The pre- 
vention of foot-and-mouth infection in vaccine virus is assured through 
federal inspection and through special tests (see vaccine virus, page 

The prevention of foot-and-mouth disease consists (1) in a cattle 
quarantine, to keep it out of countries where it does not exist; (2) in 
the elimination of the disease in cattle through isolation of infected 
herds, destruction and burial of tlie sick animals, and disinfection; 
(3) the disease in man may be avoided by care in the selection of the 
animals from which milk is taken or by pasteurization of the milk 
when foot-and-mouth disease is prevalent. 


Malta fever is a general infection not unlike other specific bacteri- 
emia, such as typhoid fever. It is caused by the Micrococcus meliten- 
sis, discovered by Bruce in 1887 during the earlier days of bacteriology. 
Clinically the disease is characterized by profuse perspiration, constipa- 
tion, frequent relapses often accompanied by pains of a rheumatic or 
neuralgic character, and sometimes swelling of the joints or orchitis. 
Malta fever is further characterized by its low mortality and long- 
drawn-out and indefinite duration. It prevails especially about the 
Mediterranean basin. 

Gentry and Ferenbaugh have recently found a nest of malta fever 
throughout the older goat-raising sections of Texas. This endemic cen- 
ter embraces an area approximately 300 miles along the Rio Grande 
extending 90 miles to the north. All the cases of malta fever found 
have occurred in territory devoted to goat raising, and all the patients 
there gave a history of drinking unboiled goats' milk or were associated 
with the goat-raising industry. The Micrococcus melitensis was isolated 
from several of the cases. ^ 

Modes of Transmission. — From experimental evidence it would ap- 
pear that the infection of malta fever may be taken in through wounds, 
the mucous membranes, or by food and drink. The usual mode of 
infection is by drinking raw goats' milk. The Micrococcus melitensis 

'"The Origin of the Eecent Outbreak of Foot-and-Mouth Disease in the 
United States," bv Mohler and Eosenau, Cir. 147, Bureau of Animal Industry, 
Dept. of Agriculture, 1909. 

V. A. M. A., Aug. 26, Sept. 9, Sept. 23, Sept. 30, 1911. 


leaves the body in various secretions and excretions. Great numbers 
of the cocci in pure cultures may appear in the urine. The milk of 
goats also contains the virus. All the secretions from the body musJD 
be regarded as infectious until further knowledge on the subject is at 
hand. In man the coccus may be isolated from the spleen, lymph 
glands, bone marrow, and mammary glands. In goats it first disap- 
pears from the blood, then the spleen, and, last of all, from the mam- 
mary glands. 

Goats are susceptible to malta fever and continue to discharge the 
infection in the milk for a long time. The disease is usually contracted 
by drinking such infected milk. While this is the common mode of 
infection, occasional cases doubtless arise through other sources; thus 
one case which arose in England is supposed to have been conveyed 
from son to father by using a clinical thermometer in the mouth im- 
mediately after its use by the patient. Monkeys may readily be in- 
fected either by the inoculation of pure cultures or by feeding them. 
At least five accidental infections have occurred in bacteriological 
laboratories, one in Washington. MacFayden lost his life from a 
laboratory infection with the Micrococcus melitensis. This microorgan- 
ism has, therefore, more than complied with all the requirements of 
Koch's laws. 

There has long been a suspicion that malta fever may be conveyed 
through the bite of an ectoparasite. In fact. Captain Kennedy was 
able experimentally to infect a monkey as a result of bites of mos- 
quitoes (Culex pipiens) which had fed on patients suffering with malta 
fever. This probably was an instance of mechanical transference of 
the infection, corresponding in all respects to a laboratory inoculation 
with fresh virulent material from a hypodermic syringe. This cannot 
be a frequent way by which the infection is transmitted in nature, for 
the specific organisms are found in small numbers in the peripheral 
blood of malta fever patients. The British Commission found the 
Micrococcus melitensis only four times from a total of 896 mosquitoes 

From the fact that the micrococcus may be successfully introduced 
either by ingestion, or by inoculation, or through the mucous mem- 
branes, it is evident that occasionally cases may receive their infection 
through a great variety of means, such as insect bites and other wounds, 
infected food, and the various modes of contact infection. Contact 
infection, however, probably plays .a minor role, for there is evidence 
that the disease is not, as a rule, directly transmitted from the sick to 
the well. There is little doubt but that the infection can be acquired 
from the urine secreted by cases of malta fever, and this is probably 
one way in which the workers in hospitals become infected. 

There is also experimental evidence to show that monkeys can be 


infected by dry dust artificially contaminated with cultures of the 
Micrococcus melitensis. The path of entrance may be through the 
nares, throat, respiratory passages, or alimentary canal. Dry dust con- 
taminated with the urine of cases of malta fever has given rise to in- 
fection in goats but not in monkeys. The experience gained during 
the work performed in Malta during 1904 and 1905 has convinced 
Horrocks that men are more susceptible than monkeys and goats. 
Shaw's work on ambulatory cases of malta fever among Maltese has 
also shown that opportunities for the creation of infected dust are 
plentiful in Malta. Infected dry dust as a mode of transmission can- 
not, therefore, be discarded, but, as a matter of fact, it probably seldom 

Goats' Milk and Malta Fever. — "We are indebted to the six reports 
of the British Commission for the investigation of Mediterranean fever 
(1905-1907) for the fact that malta fever is chiefly spread through 
goats' milk. Before the researches of this commission the common 
mode of infection was not definitely known. 

The usual source of milk in Malta is the goat. The udders, which 
are abnormally long, often touch the ground and are very liable to be 
soiled. It was first shown by Zammit in the report of 1905 that goats 
could be infected by feeding them with the Micrococcus melitensis. 
In the same year Major Horrocks discovered the Micrococcus meliten- 
sis in the milk of an apparently healthy goat. Further studies showed 
that one or more healthy goats in every herd were excreting the Micro- 
coccus melitensis in their milk and urine, and that about 50 per cent, 
of the goats reacted positively when examined by serum agglutination 
tests. All the available evidence points to their food as the main 
vehicle of infection in goats. The young goats, of course, are infected 
through their mothers milk. Horrocks and Kennedy consider that 
10 per cent, of the goats supplying milk to various parts of Malta 
excrete the Micrococcus melitensis in their milk. The excretion of 
the specific microorganism may continue steadily for three months 
without any change occurring in the physical character or chemical 
composition of the milk and without the animal exhibiting any signs 
of ill health. On the other hand, the excretion of the Micrococcus 
melitensis in the milk may be intermittent, appearing for a few days 
and then disappearing for a week or more. 

Major Horrocks in Report No. 5 of the British Commission shows 
a direct relation between the number of goats in Gibraltar to the num- 
ber of cases of malta fever. With the reduction in the number of goats 
in Gibraltar there was also a decrease in the number of cases, so that 
finally, when the number of goats had decreased to about 200 in 1905, 
malta fever had practically disappeared. 

The story of the steamship Joshua Nicholson is instructive in show- 


ing the relation between goats' milk and malta fever in man. Sixty- 
one milch goats, all healthy in appearance and good milkers (many 
being prize animals), and four billygoats were shipped on board the 
cargo steamer Joshua jS'icJiolson August 19, 1905, at Malta for pas- 
sage to the United States via Antwerp. Many of the ship's company 
partook freely of the milk. The officers drank "mixed" milk collected 
in a large vessel; the members of the crew each obtaining the "whole" 
milk from one goat in his own separate panikin. Subsequent bacterio- 
logical examination resulted in the recovery of the Micrococcus meliten- 
sis from the milk of several of the goats. Of 23 men on board the 
steamer who drank the goats' milk on one or more occasions, no evi- 
dence whatever is available as to 13, while of the remaining 10, 9 suf- 
fered from febrile attacks, 5 of them yielding conclusive e^adence of 
infection with the Micrococcus melitensis. 

Resistance. — The Micrococcus melitensis is readily destroyed by heat. 
I have shown that 60° C. for 20 minutes is sufficient to destroy this 
organism in milk and provides at the same time a liberal margin of 
safety. It is not destroyed at 55° for a short time, but succumbs in one 
hour; the majority die at 58° ; at 60° all are killed. Phenol, 1 per cent., 
destroys the coccus in 15 minutes. While this micrococcus shows a com- 
paratively feeble resistance against heat and the ordinar}^ germicides, it 
shows a remarkable resistance to dr3'ness, for it may remain alive in 
this state for months. 

The micrococcus grows well, but slowly, upon artificial culture 
media. Visible colonies do not appear until about the fifth day. It 
may be kept alive indefinitely by transplanting to subcultures at fre- 
quent intervals. Exceedingly high agglutinating power develops in 
persons suffering with malta fever — sometimes as high as 1-100,000. 
In such cases the proagglutinoid zone may appear, that is, the serum 
may refuse to agglutinate in low dilutions, such as 1-100, but aggluti- 
nate actively in higher dilutions, such as 1-1,000. 

Prevention. — Our knowledge of the cause and modes of transmis- 
sion of malta fever makes the prevention of this disease a compara- 
tively simple problem. The infection must first .be eliminated in the 
goats. Until this is done goats' milk should be pasteurized. Patients 
having the disease should be treated upon the same principles laid down 
for typhoid fever, in order to prevent the spread of the infection 
through food fomites and indirect contact. Convalescents should not 
be released until the micrococcus has disappeared from the urine. Gen- 
eral sanitary measures, such as the suppression of flies and mosquitoes, 
allaying dust, and the promotion of general cleanliness, should not be 



Leprosy is a contagious disease in the sense that it is probably 
always communicated directly from the sick to the well, but j)rolonged 
and intimate association with a leper ordinarily seems necessary to con- 
tract the infection. The degree of tlie contagiousness varies very much, 
depending upon conditions not well understood, but it is plain that 
leprosy shows little tendency to spread in any of the more highly civ- 
ilized nations practicing personal cleanliness and enjoying the benefits 
of modern sanitation. Leprosy prevailed in epidemic form in Europe in 
the middle ages, but the disease has disappeared from central Europe, 
remaining only upon the fringe of the continent, in iSTorway, Sweden, 
Spain, Italy, Greece, Turkey, Russia, and Finland. It is estimated 
that there are from 5,000 to G,000 lepers in the Philippine Islands, and 
there are many cases in China, Japan, and India. The greatest inci- 
dence is found among the natives of the Hawaiian Islands, where one 
in every 30 or 40 have the disease. Leprosy was introduced into the 
Hawaiian Islands about 1859, and there found conditions particularly 
favorable for spread. A Government Commission in 1902 ^ took a census 
of the lepers in the United States and found 278. Of these 145 were 
born in the United States and 186 probably contracted the disease in 
the United States. Of the entire number 72 of the cases were isolated 
and 205 were at large. Brinckerhofl again studied the prevalence of 
leprosy in the United States in 1909 and found 139 cases. The official 
figures for 1912 are 146. Although these numbers represent only the 
cases officially known, it is evident that the disease is not on tlie increase 
in our country and that, while it may be contracted here, it is "con- 
tagious'-' with great difficulty. There are three foci of leprosy in the 
United States : one among the Scandinavians in the region of the Great 
Lakes, another among the Orientals on the Pacific Coast, and the third 
on the Gulf Coast, particularly in Louisiana and Florida. According 
to the official health reports from our Territories and Dependencies, there 
were in 1912 in HaWaii 696 lepers, in Porto Rico 28, in tlie Philippine 
Islands 2,754, in the Canal Zone 7. The number in Guam and Alaska 
have not been enumerated. It is known, however, that many cases 
escape tabulation in the official returns. 

The cause of leprosy is the Bacillus leprce discovered by Armauer- 
Hansen in 1874. The bacillus of leprosy resembles the bacillus of tu- 
berculosis in many respects. It stains more readily and decolorizes 
somewhat more readily than the tubercle bacillus. It differs from the 
tubercle bacillus in that it grows with difficulty on artificial culture 

^ White, Vaughan, and Kosenau, Document No. 269, 57th Congress, Ist Ses- 
sion, 1902. 


media and is much less, if at all, pathogenic for the lower animals. 
Further, lepra bacilli are usually found in dense clusters and in much 
greater numbers within the cells than is the case with the tubercle 

The bacillus of leprosy grows with difhcult}- upon artificial culture 
media. For years it has evaded all attempts until Clegg ^ in 1909 suc- 
ceeded in cultivating it in symbiosis with amebse and S. cJiohrcB upon 
plain agar and weakly nutrient agar. Clegg based his work upon the 
belief that the leprosy bacillus derives its nutrition from the products 
of the tissue cells in which it is mainly to be seen in leprosy lesions. 
These results have been confirmed by Currie, Brinckerhoff, and Holman 
in Hawaii and by Duval in New Orleans. 

Immunity. — There is no racial immunity to leprosy. The white 
races suffered severely during the middle ages. Malays and Mongols 
now appear most liable to the infection, perhaps on account of their 
mode of life. The disease is remarkable for its prolonged period of 
incubation and its chronic course. These facts indicate that the body 
must possess a high degree of resistance to this infection. So far as 
known, man is the only animal subject to leprosy under natural condi- 
tions. Inoculation experiments into lower animals have recently proved 
successful in the guinea pig (Clegg); the Japanese dancing mouse 
(Sugai) ; and the monkey (Duval). 

Rat Leprosy. — There is a disease among rats which is a close coun- 
terpart of leprosy in man. It occurs naturally in the Mus norvegicus 
and may be transferred by inoculation to the more tractable laboratory 
white rat. The disease was first observed by Stenfansky in 1903 in 
Odessa. In the same year Eabinowitsch found the disease among the 
rats of Berlin, and Dean in 1903 discovered the disease independently 
in London, and in a later publication (1905) reported success in trans- 
ferring the infection by artificial inoculation. Since then rat leprosy 
has been found by Tidswell in the rats of Sydney, Australia, and the 
England Plague Commission observed the disease among the rats in 
India. Wherry and McCoy found a number of cases among the rats 
caught in San Francisco, California. 

The proportion of rats infected with leprosy in different localities 
varies greatly. Thus in Odessa from 4 to 5 per cent., in San Francisco 
0.2 per cent., and in Sydney only 0.001 per cent. Currie failed to 
find leprosy among the rats of Honolulu. The fact that the infection 
is absent among the rats of Honolulu and present among the rats in 
Berlin is evidence that it plays no part in the epidemiology of the 
human disease. 

Leprous rats in a late stage of the disease are usually recognized 

^ The Philippine Jour, of Science, Vol. IV, No. 77, Apr., 1909. FubUc Health 
Bull. No. 47, Sept., 1911. 


by the presence of patchy alopecia associated with cutaneous and sub- 
cutaneous nodules which may or may not be the site of open ulcers. 
The diagnosis is readily confirmed by microscopic examination of a 
smear from an ulcer or a nodule, which will show the specific bacillus 
of the disease in enormous numbers. 

Currie ^ has recently shown that rats may infect each other by 
contact, also that bacilli of rat leprosy may often be demonstrated in 
the heart's blood of infected rats. Currie had no difficulty in demon- 
strating the presence of acid-fast bacilli in mites contained on the 
bodies of rats when the latter's heart's blood contained the microorgan- 
isms. The fact that those mites so frequently contain the bacilli natu- 
rally leads to the suspicion that they may be one of the means of 
transmitting the disease from rat to rat. but up to the present time no 
positive evidence has been adduced that such is the case. 

In this leprosy-like disease of rats we have an infection which 
closely resembles leprosy in man. The fact that the infection may 
readily be propagated in a laboratory animal permits of its investiga- 
tion, and it is assumed that the further studies now being made upon 
rat leprosy will throw much light upon the modes of transmission 
and control of the human disease. 

Modes of Transmission. — The leprosy bacillus is found in all the 
lesions of tlie disease — the nodules on the skin and mucous membranes, 
in the spleen, liver, and testicles — in fact, in all the internal organs. 
In the anesthetic type the bacilli are found in the cells of the spinal 
cord and brain and also in the peripheral nerves. LeprOv«y bacilli may 
also be found in the circulating l)lood during the acute eruptive stage. 
Frequently they are in the endothelial or in the white blood cells. 
The leprosy bacillus leaves the body from any of the lesions that are 
broken down. From the degenerated nodules of the skin or mucous 
membranes they are discharged in enormous numbers. If we may de- 
pend upon microchemical evidence, it appears that most of these bacilli 
are probably dead. Leprosy bacilli also occasionally appear in the 
feces and urine. They do not occur in the expectoration from the lungs. 

There is some doubt as to just how the leprosy bacillus enters 
the body, whether through wounds of the skin or through the mucous 
membrane of the nose and throat or through the digestive tract, or 
possibly during coitus. 

It may be definitely stated that leprosy is not due to the eating of 
any particular food, such as fish. This theory has been stoutly main- 
tained by Jonathan Hutchinson. There is no satisfactory evidence 
in support of the fish theory and many facts against it. One thing 
is plain, and that is, leprosy is not contracted from any of the lower 

' U. S. Pub. Health and Mar. Hosp. Ser., Pub. HeaUh Bull. No. 50. Oct., 


animals, but is an infection which in all cases passes rather directly 
from man to man. 

The suspicion that parasitic insects ma}' play some role in the 
transmission of leprosy has existed for some time. The evidence is 
reviewed by IS'uttal/ who says: '"'It appears that Linnaeus and Eolan- 
der considered that Chlorops {miisca) lepra was able to cause leprosy 
by its bite." Blanchard and Corrodor tell of flies in connection with 
leprosy. Flies frequently gather in great numbers on the leprous 
ulcers and then visit and bite other persons. An observation by Boeck 
of the presence of Sarcoptes scabei in a case of cutaneous leprosy led 
Joly to conclude that these parasites might at times serve as carriers 
of the infection. Pediculi are usually present among the poor classes 
in Algeria, which furnish the greater number of lepers. Sommer of 
Buenos Aires expresses the belief that mosquitoes act as active agents 
in the spread of leprosy in warm countries. Carrasquillo of Bogota 
found the bacillus of Hansen in the intestinal contents of flies. W. C. 
Goodhue and his assistant, Father Joseph, working at the leper settle- 
ment at Moloki, found lepra bacilli in the intestinal contents of a 
female Culex pungens. Later they found similar organisms in the 
common bedbug. The British Leprosy Commission investigated the 
possible role played by insects with entirely negative results. Wherry 
studied the occurrence of lepra-like bacilli in certain flies and their 
larva. He found that the fly Chlorops vomitoria took up enormous 
numbers of lepra bacilli from the carcass of a leper rat and deposited 
them with their feces, but the bacilli apparently do not multiply in the 
flies, as the latter are clear of bacilli in less than 48 hours. Larvae 
of Chlorops vomitoria hatched out" in the carcass of a leper rat become 
heavily infested with lepra bacilli. If such larvae are removed and fed 
on uninfected meat the}' soon rid themselves of most of the lepra 
bacilli. A fly, Miisca domestica, caught on the face of a human leper 
was found to be infested with lepra-like bacilli. Most of the evidence 
bearing on the possible role of insects in the transmission of leprosy 
may be classified as purely presumptive evidence based upon analogy, 
or as evidence based simply upon the finding of acid-fast bacilli in 
certain insects. It must be plain that the simple taking up of para- 
sites by an insect does not necessarily imply that the insect plays a 
role in its transmission from one host to another. Further, all acid- 
fast bacilli are not leprosy bacilli. It cannot be denied that leprosy 
may be one of the insect-borne diseases; the final verdict will depend 
upon further studies. 

A great majority of lepers at some time in the disease have lepra 
bacilli in their nasal secretions. The importance of the nose in leprosy 
was brought into prominence at the First International Leper Confer- 

^ Johns Hop'kins Hospital Eeports, 1900, VIII. p. 1. 


ence in 1897 by the work of Sticker, who made sweeping statements 
concerning the nose as tlie site of the primary lesion and the danger 
of nasal secretions in transmitting the disease. Jeanselme and Lau- 
rans (1895), Gerber (1901), Werner (1902), Sheroux (1903), and 
others have shown the frequency with which the bacilli of leprosy ap- 
pear in the nasal secretions and the importance of the nose as a site 
of leprous lesions. Sticker cites a five-year-old child of leprous parents 
seen by him in India with an ulcer on the right side of the nasal sep- 
tum which contained lepra bacilli and was the only lesion of the dis- 
ease present in the case. Plumert (1903) mentions the finding of 
lepra bacilli in the nasal secretions of persons in intimate family con- 
tact with advanced cases of leprosy. The individuals in question showed 
no other evidence of the disease. Falkao observed epistaxis associated 
with small ulcers on the nasal septum of descendants of lepers, and 
lepra bacilli were found in the crusts from these ulcers. The results 
of Sticker, Plumert, and Falkao would indicate that in the early stages 
of the disease the nose is frequently the site of a lesion discharging 
lepra bacilli. Brinckerhoff and Moore, however, who made a careful 
study of this question in Honolulu, point out that most of the studies 
upon the importance of the nose in leprosy have been made upon rela- 
tively advanced cases of the disease. They found the nose frequently 
the seat of infection when the disease is well developed, but practically 
never as a primary or incipient lesion. If the nose were the usual seat 
of the primary lesion in leprosy, it would indicate that the infection 
is carried there upon the finger. 

Hollmann studied 500 persons in the Hawaiian Islands suffering 
with a recognizable form of leprosy for periods varying from three 
months to twenty- five years, and found 410 with lesions of the nasal 
mucous membrane and only 90 in which such lesions were absent. 

It is sufficient for practical prevention to know that leprosy is 
spread mainly by direct contact and perhaps occasionally by indirect 
contact with persons suffering with the disease. Leprosy is most preva- 
lent under conditions of personal and domestic uncleanliness and over- 
crowding, especially where there is close and protracted association be- 
tween the leprous and the non-leprous. There is no evidence that 
leprosy is hereditary. The occurrence of several cases in a single fam- 
ily is doubtless due to "contact."' The danger of infection from leprous 
persons is, of course, greater when there is a discharge from the le- 
sions of the skin and mucous membranes. 

Prevention. — The prevention of leprosy depends almost entirely 
upon isolation, care of the infected discharges, personal cleanliness, 
and sanitary surroundings. That the disease is transmitted with dif- 
ficulty is shown by the fact that doctors, nurses, sisters of charity, 
ward tenders, and others directly exposed in leprosaria seldom become 


infected. Xotable exceptions have been Father Damien in Honolulu 
and Father Bogliolo in Xew Orleans. Evidently close, prolonged and 
intimate contact is ordinarily necessary to contract the infection. For 
many years a case of leprosy was cared for as a patient in a hospital 
with which I was associated. He had his own dishes, towel, soap, etc., 
otherwise he mingled freely with the patients and others, without 
spreading the disease. 

For the control of leprosy the most important administrative meas- 
ure is to segregate the lepers in settlements or asylums. Compulsory 
notification of every case of leprosy should be enforced, if for no other 
reason than to keep track of the disease and to know whether it is on 
the increase. Segregation of lepers is the most important single pre- 
ventive measure. The leprosaria should be inviting and should con- 
tain all modern improvements for the care and treatment of the 
disease. Leprosy is by no means invariably fatal. In the United 
States, where there are only a few hundred lepers, the Government 
should establish a national leprosarium conducted upon the principles 
of a modern sanitarium for tuberculosis. To require each state to 
provide suitable accommodations to segregate its few lepers is econom- 
ically wasteful. It is claimed that the decrease in leprosy in Europe 
since the middle ages has been due in large part to the segregation 
of the lepers in leprosaria, which at one time numbered 20,000. On 
the other hand, the value of segregation in countries where leprosy is 
very prevalent is disputed. As a rule, only the advanced cases are 
detected and isolated. Segregation in the Hawaiian Islands has so far 
had no effect upon the prevalence of the disease. There are factors in 
the control of leprosy not yet understood. 

There can be little objection in a country such as ours, where leprosy 
shows slight tendency to spread, to give a clean leper his freedom. 
There is no more danger from a leprosy patient of clean personal 
habits, who exercises care concerning the discharges from the lesions, 
than there is from a discharging case of tuberculosis of the glands of 
the neck. 

The national quarantine regulations forbid the landing of an alien 
leper. The law requires that such person be deported on the same ves- 
sel that brought him. A citizen of the United States having leprosy 
cannot be debarred. Such individuals are admitted and then come un- 
der the health laws of the state or port of entry. 

Specific Prevention. — There is no specific prevention or cure for 
leprosy. Xastin is a substance proposed by Deycke and consists of a 
neutral fat obtained from a streptothrix. The reports from its use 
are not particularly encouraging. Eost, of Bangoon, Burmah. uses 
a substance which he calls "leprolin," a precipitate from leprous tu- 
bercles. Tuberculin in somewhat large doses injected subcutaneously 


into leprous patients produces both a general and local reaction, but 
the repeated injections do not materially influence the disease, although 
such treatment seems to cause a local improvement or softening of the 
leprous tubercles. Heiser in Manila reports favorable results from the 
aj)plication of X-rays. Dyer in Louisiana has obtained good results 
from good food, fresli aii\ (leanliness, and the general principles applic- 
able to the modern treatment and prevention of tuberculosis. 


By Thomas W. Salmon, M.D. 

Passed Assistant Surgeon, U. 8. Public Health Service; Director of Spe- 
cial Studies, National Committee for Mental Hygiene; Formcrli/ 
Chairman of the New York State Board of Alienists. 

Although, in the prevention of insanity, we have to deal with prob- 
lems more complex than those which have been considered in the 
prevention of the infectious diseases, some mental diseases are known 
to depend upon causes as definite as the infection of the body with 
pathogenic bacteria. We know, for instance, that if a patient with 
one of the alcoholic psychoses had not been addicted to the use of al- 
cohol he would not have acquired this mental disease, whatever other 
bodily or mental infirmity he might become afflicted with, for recent 
methods of studying mental diseases have made it possible to recog- 
nize certain groups of symptoms which can be produced by alcohol 
and by that cause alone. There are clinical symptoms and laboratory 
findings which enable us to learn, with small chance of error, that a 
patient is suffering from general paresis. We know that such a pa- 
tient owes his mental disease to syphilis, and that for him the preven- 
tion of insanity would have consisted in the prevention of syphilis. 

Not all types of mental diseases, however, have causes so well un- 
derstood as these. There are many in which the pathology is unknown 
and in which the symptoms are so variable that at present we are 
obliged to place them in provisional groups from which we may be 
able to rescue them later, perhaps, when present diagnostic difficulties 
have been overcome or when new light has been thrown upon their 
nature. It seems desirable, in discussing the preventable causes of 
insanity, to consider first some of the factors which -we know are ca- 
pable of producing mental disease, either directly or indirectly, at the 
same time referring to possible means for their control, and then to 
consider some other causes which we have excellent reasons for believ- 


ing influence the prevalence of insanity, but which operate in a man- 
ner which cannot be shown so conclusively. 

It is essential to state at the outset that a number of different 
diseases are included in what we term "insanity." It would be quite 
permissible to speak of the various mental diseases as "insanities," so 
greatly do they vary in their symptoms, course, and etiology. Just 
as the popular term ^^leart disease" properly includes congenital malfor- 
mations, changes associated with acute infectious diseases, reactions to 
toxic substances, disturbances of the nervous mechanism, and the ef- 
fects of disease of remote organs, so "insanity'" includes diseases de- 
pendent upon congenital mental deficiency or developmental defects, 
.the exhaustion accompanying acute or chronic disease, the introduction 
of toxic substances into the body or their elaboration within it, organic 
changes in the brain, and abnormal psychic reactions. 


It seerns desirable to consider infectious diseases as a cause of 
mental disease first, not because they are responsible for a larger pro- 
portion of cases than other preventable causes, but on account of their 
closer relation to that with which we are familiar in the realm of pre- 
ventive medicine. 

Typhoid fever may give rise to permanent or transitory mental 
impairment. The prevention of insanity in this instance consists, of 
course, in the prevention of typhoid fever. When the evils resulting 
from the needless prevalence of that disease are counted up, the cases 
of mental disease caused by it must be included. 

Other infectious diseases, notably influenza, scarlet fever, malarial 
fever, erysipelas, and septicemia (particularly from uterine infection), 
furnish a considerable number of cases of mental disease, chiefly in 
the infective-exhaustive group, in which exhaustion, elevated tempera- 
ture, and poisoning of the nervous centers by bacterial toxins are the 
immediate causes of mental changes. About three per cent, of all 
first admissions to hospitals for the insane ^ belong in this group. It 
is impossible to estimate the proportion of cases in which infectious 
disease is the only cause in other types of mental disease, for an acute 
infection may "^^iberate" an attack in a patient subject to a psychosis 
in which recurrences are common, and this cause may combine with 
others, alcohol, for instance, in the production of a psychosis in which 
the infectious disease plays a secondary part. 

^ This percentage and others following are based upon recent statistical 
studies of admissions to the state hospitals of New York and Massachusetts. 
About one-fourth of all the insane under treatment in the United States are 
patients in the public institutions of these two states, and statements based upon 
the statistical studies in question are fairly applicable to the United States as a 


Preventive measures in such types of insanity must consist chiefly 
in the general work of limiting the prevalence of the infectious dis- 
eases, but much can be done by improved methods of treating febrile 
conditions. The full significance of delirium and its pathology must 
be appreciated and hydrotherapy employed more generally and more 
carefully if we are to lessen the number of patients with infective- 
exhaustive psychoses. The indiscriminate use of sedatives or hypnotic 
drugs in deliria sometimes results in an aftermath of mental disease. 

Syphilis deserves separate consideration as a preventable cause of 
mental disease, for it is the essential cause of general paresis, a disease 
responsible for about 13 per cent, of all first admissions to hospitals 
for the insane in this country, and for nearly one-fifth of all male 
admissions. In admissions from American cities more than 22 per 
cent, of male patients are suffering from general paresis. More deaths 
resulted in New York State from general paresis in 1911 than from 
smallpox in the whole registration area of the United States since 1908. 
Half as many deaths are known to occur every year from general pare- 
sis as from typhoid fever. It is believed that a considerable number 
of deaths from general paresis, when occurring outside of institutions, 
are reported as "softening of the brain" or by some other indefinite 
term, and the prevalence of general paresis is, therefore, far greater 
than mortality statistics would indicate. 

This disease runs a uniformly fatal course, the average duration 
of which is from two to five years. It attacks people who have, to all 
appearances, recovered from syphilis, and most frequently in the fourth 
decade of life, when their usefulness to the community and to their 
families is greatest. It is the grimmest specter which follows youth- 
ful indiscretions and "sowing wild oats." Of course, the prevention 
of general paresis depends wholly upon the prevention of syphilis, a 
well-defined field of effort in preventive medicine, but it seems that 
impetus would be lent the movement for venereal prophylaxis if the 
appalling prevalence of this result of syphilis were more widely known. 
It is a rather surprising fact that many of those actively engaged in 
the campaign against venereal disease are quite unaware of the preva- 
lence of general paresis or that it depends upon previous infection with 
syphilis. It is a fact that general paresis is a much more frequent 
manifestation of syphilis than locomotor ataxia.^ 

' It is very desirable to know what proportion of eases of syphilis result in 
general paresis, but, until recently, no satisfactory studies had been undertaken 
to determine this, and, on account of the long interval between infection with 
syphilis and the development of symptoms of general paresis, it seemed impossi- 
ble to find a group of population in which such studies could be made. A short 
time ago, however, Mattauschek and Pilcz made public (Berliner I'linische Woch- 
enschrift, Feb. 19, 1912) the results of a careful examination of the histories 
of 4,134 officers of the Austrian Army who had contracted syphilis during the 
period 1880-1890. They ascertained that 4.67 per cent, of these ofiicers developed 
general paresis. 


A small number of cases of other types of mental disease are also 
directly the outcome of syphilis. Mental deterioration is associated 
with gunimata of the brain and mental changes accompany local menin- 
gitis due to syj^hilis. Syphilis is also responsible for a certain propor- 
tion of cases of congenital mental defect upon which insanity may 
become engrafted later, and it is often syphilis which first attacks the 
integrity of the arterial wall, thus laying the train destined 
to result, years later, in arteriosclerosis and mental disease dependent 
upon it. 

Tuberculosis is a cause of mental disease much less frequently than 
has been supposed. It is exceedingly doubtful if, as has been asserted, 
tuberculosis ever results in a special clinical form of mental disease, 
but the exhaustion of a chronic, wasting illness and the action of the 
tubercular toxin upon the nervous centers are probably immediate 
causes of mental changes. Although there are no especial measures 
of prevention of mental disease dependent upon tuberculosis, the fact 
that this is one of its possible effects might well be added to the in- 
formation disseminated regarding tuberculosis, for not the least of the 
benefits from curing incipient cases or preventing the spread of tuber- 
culosis is that the prevalence of insanity is thereby even slightly les- 

Pellagra. — It is hardly justifiable, perhaps, to speak of pellagra as 
a preventable disease when the ground is just being cleared for a satis- 
factory search for its cause, which at present is assumed to be spoiled 
corn (see page 577). With the practical application of means for the 
control of this disease, a certain number of cases of insanity will be 
prevented in the localities where pellagra prevails. 


Alcohol. — It is a strange commentary upon human frailty that all 
the poisons which assail man through accident and the dangerous 
trades in which he must engage, and all the poisons which are elabo- 
rated within his system, as in nephritis, diabetes, thyroidism, and ac- 
romegaly, are together responsible for but a small fraction of the num- 
ber of cases of mental disease due to his deliberate ingestion of one 
poisonous substance — alcohol. 

It is likely that alcohol, as a predisposing or as an immediate 
cause, is responsible for more than a third of all admissions to our 
hospitals for the insane. When, however, we consider alcohol as a 
cause in diseases in which other etiological factors enter, we are upon 
ground where statements must be made with caution and with many 
qualifications. Thus a man with a considerable degree of congenital 
mental defect is induced by some companions to take a few drinks 


of wliiskey, and he thereupon develops an episode of excitement which 
lasts several months. Alcohol is not the most prominent feature in 
such cases, perhaps, and yet if it is withheld such persons might never 
develop acute mental symptoms. In considering alcohol as a cause 
of mental disease it seems best to confine ourselves at first to those 
diseases which, from their symptom-complexes, we have come to rec- 
ognize as the alcoholic psyclioses. In these disorders, acute alcoholic 
hallucinosis, chronic alcoholic insanity, and Korsakow's disease, to 
diagnose the disease is to know the cause, About 12 per cent, of all 
first admissions are for these psychoses. 

They are met in men about three times as frequently as in women, 
and, as in the case of general paresis, more frequently in admissions 
from cities than from the country, although there is by no means as 
much disparity. These alcoholic psychoses are the direct, unmistak- 
able results of intemperance, acting in many cases upon psychopathic 
individuals, but it is believed that in less direct ways alcohol is re- 
sponsible for nearly as large a share of admissions to hospitals for 
the insane. In the year ending September 30, 1909, alcohol was as- 
signed as an etiological factor in 31.4 per cent, of the men admitted 
to the New York State hospitals, and in 9.6 per cent, of the women. 
As a habit disorder, but not a definite etiological factor, intemper- 
ance was reported in 14.3 per cent, of cases among male admissions 
and 6.1 per cent, among female admissions. So 45.7 per cent, of all 
the men admitted and 15.7 per cent, of all the women admitted were 
addicted to the excessive use of alcohol. This is a prevalence of intem- 
perance enormously greater than in the general population, but it 
must be remembered that not a few patients admitted to institutions 
for the insane had become intemperate as a result of mental disease, and 
a great number, including those with alcoholic psychoses, as a result of 
constitutional mental inferiority. The idea is spreading among psychi- 
atrists that, iti a world of drinkers, the alcoholic is an abnormal type. 
This fact does not in any way lessen the importance of alcohol as a 
cause of mental disease, but it shows the great necessity of throwing 
especial safeguards about unstable persons in whom intemperance may 
lead to such disastrous results. 

There is hardly a mental disease which is not influenced unfavor- 
ably by alcoholic habits. They lend a tremendous impetus to the retro- 
gressive changes in senility, and, as has been said, the acquisition of 
alcoholism by defectives often results in acute mental symptoms when 
none need have occurred. Statistics collected independently by several 
investigators show that the parents of nearly 50 per cent, of defective 
children were alcoholics. It is held by many psychiatrists that no other 
single cause of imbecility and idiocy except mental defectiveness in the 
parent can compare with alcoholism in the parents, intemperance of 


mothers during pregnancy being thought to be particularly likely to 
result in mental defect in the offspring.^ 

The prevention of mental diseases due to alcohol, like the preven- 
tion of those due to ' syphilis, is only part of the general movement 
against these enemies of the race. Excluding poverty and crime, there 
is probably no more disastrous result of alcoholism than the continual 
procession of unfortunates who are entering hospitals for the insane 
because of intemperance, and it is certain that no other fatal termina- 
tion of syphilis is so frequent as general paresis. 

Other Exogenous Poisons. — Morphinism and other drug addictions 
are responsible for less than one per cent, of first admissions to hos- 
pitals for the insane in this country. Fewer such patients are ad- 
mitted in ISTew York and Massachusetts now than were a few years 
ago. This gratifying fact is due, in part at least, to stricter enforce- 
ment of the laws regulating the sale of narcotics and particularly to 
the pure food laws which have rendered it a little more difficult to 
dispense habit-forming drugs in patent medicines. It is well within 
our power to eliminate this cause of mental disease by wise legislation 
and its rigid enforcement. 

A very small proportion of' admissions is caused by occupational 
poisonings, such as lead and carbon monoxid. This small proportion can 
be still further reduced by increasing attention to measures safeguard- 
ing workmen in dangerous trades. 

Endogenous Poisons. — Those poisons originating within the system 
which produce mental disease are for the most part the result of other 
diseases, and these diseases — nephritis, heart diseases, and diabetes — 
are, unfortunately, beyond the reach of preventive medicine. When 
the infectious diseases have come under our control, and when means 
have been devised to reduce accidents to a minimum, the preeminence 
of these diseases as causes of death will only be accentuated. 

In the case of psychoses dependent upon diseases of the thyroid 
gland, early treatment of the primary disease is a hopeful means of 
prevention. It is curious that vaccines and sera should be furnished 
free by the state while any person can remain mentally defective from 
cretinism, because prolonged treatment is too expensive. The state 
has such an enormous number of the insane and mentally defective 

^ It should be said that recent studies by the Francis Galton Laboratory 
of Eugenics, London, point to directly opposite conclusions. The weight of 
evidence, however, is in favor of the relation between alcoholism and mental 
defect indicated above. Bezzola and Hartmann state that examinations of the 
birth-dates of idiots and imbeciles in Switzerland show that conception recurred 
in a large proportion of cases at seasons of the year when the celebration of 
certain festivals were accompanied by much intoxication. It is said that this is 
popularly recognized and that such children are known in certain districts as 
rauscJcinder ("jag-children")- On the other hand, the birth-dates of defective 
children in certain fishing villages in Northern Europe where there is much peri- 
odic intoxication have been carefully studied a,nd no such relation discovered. 


for whom permanent care must be provided that it would be a matter 
of sound policy to seek out such cases and then provide the best care 
and treatment absolutely without cost. 


A considerable number of the cases admitted to every large public 
institution present a history of head injuries, usually with fractures of 
the skull. There are certain syinptom-coniplexes especially frequent in 
such cases, and so it can be said that injury of the brain is a specific cause 
of mental disease. Street accidents, railroad accidents, and unprotected 
machinery are by far the most frequent causes of head injuries in civil 
life. It is quite justifiable to consider this cause of insanity as pre- 
ventable, for one has only to read the recent literature on safeguarding 
workmen in factories and protecting railway employees to see that this 
is a field in which much may be done. Street accidents have been 
practically eliminated in some cities by efficient police regulation of 
traffic. In a consideration of the prevention of insanity this phase is 
not sufficiently important to receive much space, and yet it seems de- 
sirable to mention it. 


It is probably safe to say that none of the causes of insanity which 
have been considered, unless it be alcohol, is as important a factor as 
heredity, and heredity enters largely into the production of alcoholism, 
or, at least, into the production of the mental type wliich succumbs to 
alcohol. Opinion as to the influence of heredity upon the development 
of mental disease has undergone much change in recent years, as it has in 
reference to other diseases, but it can be said that studies which have 
led to heredity being considered of secondary importance in some con- 
ditions in which it was thought to be paramount have been offset by 
studies in other directions which have disclosed heredity as a factor of 
the greatest importance. Studies are actively under way to determine 
the relation of Mendel's laws to heredity in insanity. In large series 
of admissions for all forms of mental disease in this country and in 
Europe it has been found that, in the cases in which a satisfactory 
history was obtainable, about 50 per cent, of the patients had an insane 
heredity. There are no statistics available in this country to show the 
proportion of normal people with an insane heredity, but Kraepelin 
quotes Jost as giving the percentage as 3 and Nacke as giving it as 7.5. 
There are some mental diseases in which the percentage of insane 
heredity is only slightly more than this, while in manic-depressive insan- 
ity the percentage has been found in a large series of cases to be as high 
as 70, many of the insane ancestors having other forms of mental disease. 


This shows very interestingly the unity of some of the factors which 
underlie mental diseases of different types. 

Without discussing the influence of heredity further, some possihle 
means of prevention may be considered. This is the domain of eugenics. 
The means suggested all have for their object either the permanent 
sequestration of the insane and mentally defective or the prevention 
of offspring by control of marriage or by sterilization. It has been 
proposed by some that it should be required by law that no woman in 
the child-bearing period who secures admission to a hospital for the 
insane for a psychosis in which heredity is known to play a prominent 
part should be discharged, even if recovered, until the menopause has 
been reached, and it is asserted that the welfare of the race justifies 
such a procedure. It cannot be denied that such a course might in time 
effect some reduction in the prevalence of mental diseases. It would 
seem that society can find justification for adopting some such measures 
to protect itself in those cases in which every period of parole or dis- 
charge from a hospital is followed by a pregnancy, but the ethical con- 
siderations involved are so complex that it is sufficient here merely to 
state this proposal. It has been proposed to sterilize by vasectomy or 
other means all patients when they are about to be discharged from a 
hospital for the insane, if their mental disease was of a type in which 
heredity is prominent. Here again there are complex ethical questions 
to be considered, but, as an alternative, it may be suggested that all 
such patients should at least he offered the opportunity of providing 
against such an occurrence. It is believed that, if the matter were 
tactfully and earnestly presented, the freedom from danger pointed 
out, or even a small bounty paid by the state in suitable cases, there 
would be a considerable number of acceptances. 

Prohibiting the marriage of those in whom insane heredity within 
a close degree of relationship exists would depend for its effectiveness 
upon the provisions for obtaining such information and any such meas- 
ure would be practically without value unless it were required in a 
number of states. Education as to the dangers of heredity and appeal 
to social conscience, by physicians, teachers, and clergymen, would un- 
doubtedly deter a few from marriage, but it is the experience of physi- 
cians generally that such advice is rarely heeded. Before the matter 
can be presented in a "campaign of education" there is need for far 
better information than we possess at present. Facts should be most 
carefully sifted and statistical studies of broad scope undertaken under 
the auspices of the government or some national society before infor- 
mation regarding heredity and insanity is prepared for wide dissemina- 



During the last few years the psychical causes of insanity have been 
recognized as of great importance, and types of mental disease which 
were thought to be almost wholly dependent i^pon the constitutional 
make-up of individuals have been sliown by P'reud, Jung, Meyer, Hoch, 
and others to be dependent very largely upon errors of education, un- 
suitable environment, the acquisition of injurious habits of thought, 
and the suppression of painful experiences, usually in the sexual field, 
which later in life form the basis for psychoses. The outlook for the 
prevention of insanity is very hopeful in some of these cases in the 

Emphasis must be placed upon the important fact that the founda- 
tions of aberrations in wliich sexual trends are prominent are laid at 
an extremely early age. It is only very recently that it has been shown 
that experiences in childhood and infancy exercise a controlling influ- 
ence upon the sexual life of later years. Tlie practical application of 
this is not that children are to be brought up in seclusion, but that 
there is no higher duty of parents than to establish such relations with 
their children that sex difficulties can be discussed and straightened 
out before they give rise to permanent moods or trends. Hypocrisy 
and false shame are not natural attributes of the child, and when we 
create them we raise a barrier behind which much damage may take 
place without our knowledge. In childhood and in adolescence there 
must be established the closest bonds of sympathy and understanding 
between parent and child. Wholesome, frank communication and sen- 
sible consultations at that time regarding sex quandaries may save a 
child or young adult from disaster later on. In the aberrations which 
come with adolescence one can usually recognize the results of early 
mismanagement in these matters, and the urgent need for sound ad- 
vice and correct guidance needs no elaboration. 

In dispensaries for "border-line"' cases some hidden sexual trends 
or other factors in psychogenesis may be discovered, and preventive 
measures prove successful. Nothing could aid more in the discovery 
of such factors than general appreciation by physicians that they may 
exist and may result in insanity. If there were such general recogni- 
tion of the part such factors play many persons not insane would be 
referred to the psychiatrists and more psychiatric clinics would be 


Unemployment, overwork, congestion of population, child labor, 
and the hundred economic causes which increase the stress of living 


for the poor are factors in the production of insanity which often seem 
to outweigh all others. Weaknesses in constitutional make-up — de- 
fects in the armor of personality — are disclosed under the stress of such 
conditions which would have remained undiscovered under happier cir- 
cumstances. All that can be said of the prevention of such causes is 
that everything which makes for the betterment of those upon whom 
the stress of living falls heaviest will save many from mental disease. 
For the individual careful training, encouragement, wise counsel, and 
a little financial assistance in times of especial need are helpful meas- 
ures. If the operation of these powerful causes cannot be prevented, 
those who are most likely to be harmed would, perhaps, be shielded a 
little if the dangers which they face were more generally known. 


No consideration of the preventable causes of insanity in this coun- 
try would be complete without reference to this important element in 
our national life. It is a question peculiar to the United States. Since 
1820 more than 28,000,000 immigrants have come to this country. 
This vast migration has no parallel in history. In some states the 
increment to the population from immigration every year exceeds that 
from births. Under such conditions movements such as those directed 
against alcohol, heredity, or the economic causes of insanity are feeble 
compared with a thorough sifting of applicants for admission while 
they are still at our threshold. We have the absolutely unquestioned 
right to require any reasonable tests which can be proposed, and yet 
the present immigration law results in the mental examination of only 
one in every thousand of the million immigrants who seek admission 
each year. There is no provision whatever requiring immigrants to 
present certificates from responsible authorities at home, testifying to 
their freedom from mental disease. These crowds of immigrants, 30 
per cent, of the adults illiterate and less than 20 per cent, with any 
trade, are, practically without mental examination or selection, projected 
into our most congested centers of population, to bear, during their 
first year in America, as severe stress as any group of population can 
be called upon to endure. One result is that they flood our hospitals 
for the insane. Hundreds have to be returned during the first year 
for mental disease due to causes which existed before their arrival. In 
the succeeding years the proportion rises and in the next generation 
and the one succeeding it we shall reap the harvest for which our pres- 
ent policy is sowing the seed. It can be earnestly asserted, after long 
study of this question, that no measures for the prevention of insanity 
which have yet been suggested can prove so efficacious as artificial 
selection of accretions to our population, on the vast scale which an 


adequate mental examination of immigrants would permit. This is a 
measure of practical eugenics which can be applied as successfully now 
as in a generation. As Professor R. DeC. Ward has said, "it is merely 
a question whether we or foreign steamship agents shall select the 
parents of future generations of Americans." The provisions of the 
federal immigration law which deal with the exclusion of insane immi- 
grants are in need of thorough and immediate revision, and the enforce- 
ment of the law should receive the attention which its importance 

We have been far too careless of the welfare of recently landed 
immigrants. There seems to be a general impression that, however 
unsanitary their surroundings or however heavy may be the burdens 
placed upon them, immigrants are, in some way, fitted for such hard- 
ships, either by nature or through previous experiences in their homes. 
Of course, this assumption is wholly without justification, and it is 
time that the social, economic, physical, and moral welfare of these 
newcomers be given the earnest attention of the federal and state gov- 
ernments and of societies and individuals. By so doing something 
may be done to lessen the terrible prevalence of mental disease in this 
large group of our population. 


It is possible to outline only very briefly the agencies which can 
be utilized in the application of preventive measures. 

Hospitals for the Insane. — A very large proportion of the insane 
persons in any state will be found under treatment in public institu- 
tions. This is not the case with other diseases, sufferers from which 
are widely scattered, in their homes, at work, and in hospitals. This 
fact makes the hospital for the insane seem the logical place from 
which preventive measures should emanate. 

Every large hospital for the insane, unless entirely inaccessible, 
should maintain a dispensarv'. To that dispensary, if it is skillfully 
conducted with its broadest aims constantly in mind, will come in- 
cipient cases, "border-land'' cases, those who have had previous attacks 
of mental disease, and relatives seeking advice. Such dispensaries — 
and several have already been instituted — afford rich opportunities for 
the practical application of preventive measures and for the dissemina- 
tion of information. Members of the hospital staffs should also engage 
in field work in the districts from which their hospital receives its pa- 
tients. Talks on the preventable causes of mental disease, the advan- 
tages of earlier treatment, and the necessity of considering insanity as 
a disease and not a crime can be given by such medical field workers in 


schools and churches and before clubs and societies. Such talks should 
be supplemented by illustrated descriptions of modern methods of caring 
for the insane and promoting their happiness and comfort. It is 
usual for citizens to haA'e a local pride in their hospital as a public 
institution, and this will often insure interest. Every such lecturer 
■vrill be quite sure to have the relatives or friends of some of his patients 
among his hearers. Such field work by physicians should be supple- 
mented by that of well-trained social service workers permanently at- 
tached to the institution. 

The hospital should also be the center for instruction in clinical 
psychiatry in the community. The great wealth of clinical material 
in a large hospital for insane should be utilized to the fullest extent 
if a medical school is near enough, but it is believed that better knowl- 
edge of mental diseases in this country will be brought about much 
more effectively by developing the opportunities of the general practi- 
tioner for receiving instruction than by increasing very greatly the 
time devoted to psychiatry in medical schools. The medical student 
is often overburdened, and he has much difficulty in deciding upon the 
relative value of the matters presented to him. In competition with 
other branches of medicine psychiatry is very apt to fare badly, for it 
is likely to be regarded as a specialty of slight value or interest to one 
who is about to engage in general practice. With the practitioner it 
is different, for he is a dull man who does not learn early in his career 
that mental diseases are frequently met with and are very important 
in many of their relations. It is a fact that there is no opportunity 
in the United States for a graduate in medicine to obtain post-graduate 
instruction in psychiatry unless he is a member of the staff of an in- 
stitution for the insane or a medical officer of one of the government 
medical corps. 

The hospital for the insane has many opportunities for instructing 
general practitioners. Frequent medical meetings at the hospitals, in 
which clinical talks should have chief place, correspondence with physi- 
cians who sign commitment papers regarding interesting features or 
the course of their cases, invitations to necropsies (which in most small 
communities will be gladly accepted), and consultations when patients 
are about to be discharged, at which suggestions for after-care can be 
made, are all means of interesting physicians in mental diseases and 
their prevention. All these new tasks, which are certain to be assigned 
to our hospitals for the insane within a few years, will necessitate ad- 
ditional medical officers, and they make it more necessary than ever 
that clinical and laboratory work in these institutions should be upon 
a high plane. This means increased appropriations, but it is doubtful 
if a state can utilize its funds for a better purpose than in fostering 
the work of prevention in mental diseases. Placed upon a purely eco- 


nomic basis, such work is immensely profitable. It has been estimated 
that prevention of the admission of a single patient each year would 
yield a return to a state larger than the pay and exj)enses of two social 
service field-workers for a year. 

The hospital has also excellent opportunities for disseminating in- 
formation among the laity regarding the cause and prevention of in- 
sanity. Leaflets, personal talks, and general literature regarding these 
subjects will not fail to interest those who have come to the hospital 
to visit a near relative. 

Central Boards of Control. — In most states the administration of 
hospitals for the insane is in some measure under the control of a cen- 
tral board. Such bodies can do much in the prevention of insanity. 
In many states they can require such activities on the part of the hos- 
pitals as have been outlined, and in others they can exert powerful 
moral influence in having them undertaken. They can conduct statis- 
tical studies as to the preventable causes of insanity, and secure wide 
distribution of the material collected. They can suggest and urge legis- 
lation for the early treatment of the insane and for the adoption of 
specific preventive measures. They can, particularly by cooperation 
with similar authorities in other states, secure some reforms. in federal 
legislation regarding the exclusion of insane and mentally defective 
immigrants, the urgent need for which ha? been pointed out. 

National and Local Societies for Mental Hygiene. — Tliere is a very 
clearly defined field of effort for national and local societies in the 
work of prevention of mental diseases. As has been indicated, the care 
of the insane is, far more than that of any other class of the sick, in 
official hands. There is besides a great deal in the methods of com- 
mitment and provisions for care, which is regarded wholly as an offi- 
cial matter. For this reason there is decided need of agencies which 
can bridge the gap between tiie home and usual environment of the 
patient and the public institution which is charged witli his care. A 
certain part of the social service work which has so useful a place 
in the care of the insane, particularly in the period following discharge 
from institutions, should be done by workers under the direction of 
institutional authorities, but there is also a very great deal which can 
be done better by societies cooperating with institutional authorities 
but not officially connected with them. In New York State the "Com- 
mittee on Mental Hygiene" of the State Charities' Aid Association 
has a local committee in each hospital district. Although after-care 
and efforts to improve the kind of care afforded the insane in that criti- 
cal period while commitment is pending constitute the chief work of 
such committees, there is often opportunity for effective work in pre- 
vention. In Connecticut, Illinois, and Massachusetts there are state 
societies of mental hygiene doing most useful work. 


There is a National Committee for Mental Hygiene, coordinating 
and, in a measure, directing these local activities. This committee has 
commenced studies into existing provisions for the care of the insane 
in all the states, methods of commitment and care, the influence of 
preventable causes, etc. With a carefully prepared plan of work, ac- 
curate information is to be obtained upon these matters, and, as fast as 
the facts in the possession of the committee justify it, active work is 
to be undertaken for amelioration or prevention. It is believed that 
a great deal can be done, especially in the direction of standardizing 
work for the care of the insane and the prevention of insanity, and in co- 
ordinating the efforts of the hospitals, state boards of control, and some 
of those organizations which sometimes, perhaps unawares, are attack- 
ing preventable causes of insanity from different angles. Such an 
organization as the National Committee for Mental Hygiene can stimu- 
late interest on the part of the state and local authorities charged with 
the care of the insane, and it can sustain interest when it might other- 
wise flag. Standards established in a state where advanced ideas prevail 
can be made known in states where there is indifference or lack of prog- 
ress. A central "clearing house" for the collection and distribution of 
accurate information regarding the care of the insane and the preven- 
tion of insanity can be provided. Earlier treatment and the transfer of 
care pending commitment from the policeman to the doctor — the most 
urgent needs of the insane — can be secured by this organization, and 
the lamentable failure to provide instruction in mental diseases in the 
medical schools can be shown, and the means suggested for remedying 
the defect. It is a fact that the number of beds in the institutions for 
the insane in this country is greater than the number of beds in all the 
general hospitals of the United States. The insane are, therefore, the 
most numerous class of the sick receiving public care. As such, they 
demand a large share of the interest of every practitioner. Progress in 
every branch of preventive medicine depends most upon the efforts of 
physicians, and in this particular field there is need of much wider in- 
terest on the part of the medical profession than exists to-day. 

Education. — Under the direction of state boards of control and en- 
couraged by national and state societies for mental hygiene, much can 
be done toward placing the education of defective children upon a bet- 
ter basis. These children are now chiefly interesting to school authori- 
ties, for they constitute a special class and should receive separate in- 
struction, both for their own good and the good of normal children, 
whose progress is retarded on account of the excessive amount of time 
teachers must give defective children. They should have a far greater 
interest for the state than this, for eveiy such child is a possible patient 
in a hospital for the insane or in a colony for the mentally defective. 
Every effort to prevent this outcome is justified, and it would seem 


desirable for the state to provide very liberally for the study of these 
children and for their education. Of even more importance, perhaps, is 
the permanent segregation of most of them. 

It has been estimated that in a state which adopts a high standard 
of caring for the insane about one-fifth of the annual income of the 
state will be required. Whether insanity is increasing or not, the num- 
ber of the insane under treatment has, up to this time, increased much 
more rapidly than the general population. New demands for charitable 
and social purposes are constantly being made upon state funds, but 
it would seem that any measures for the prevention of insanity which 
offer hopes of success should receive the substantial financial support 
of the state. 

The attempt has been made to outline some of the preventable 
causes of mental disease and to indicate, very broadly, possible pre- 
ventive measures. It seems essential that, notwithstanding the com- 
plexity of some of the questions involved, the prevention of mental 
diseases should be considered in the general advance which is being 
made against microbic diseases, for it is very closely related to all the 
other fields of preventive medicine. Recent advances in the field of 
psychiatry have, upon the whole, given grounds for encouragement, for 
if the outlook in some directions is not bright the accuracy with which 
the part played by certain causes has been defined promises much. The 
fact that it has been definitely determined that there are certain essen- 
tial causes of mental disease, and that some of these essential causes 
are entirely controllable, makes it imperative that preventive measures 
be undertaken. 


Sources of Infection. — There are two great sources of the commu- 
nicable diseases of man, viz.: (1) man himself, and (2) the lower 
animals. Most of the communicable diseases of man, especially those 
which occur in epidemic form, are peculiar to man. This is the case 
with typhoid fever, cholera, leprosy, malaria, yellow fever, syphilis, 
mumps, measles, scarlet fever, typhus fever, infantile paralysis, small- 
pox, chickenpox, relapsing fever, dengue, and even tuberculosis in large 
part. It is quite true that some of these infections may be communi- 
cated to the lower animals under experimental conditions, but they do 
not, as a rule, occur in them under natural conditions. In other words, 
most of the communicable diseases from which man suffers are specific ; 
the degree of specificity varying slightly with the different infections. 

It is, therefore, plain that man is the great source and reservoir of 
human infections. Man is man's greatest foe in this regard. The fact 
that most of the communicable diseases must be fought in the light 
of an infection spread from man to man is one of the most important 
advances in preventive medicine. This new thought has crystallized 
out of a mass of work in the sanitary sciences during the past decade, 
especially from researches upon tuberculosis, typhoid fever, cerebro- 
spinal meningitis, and other communicable diseases. Formerly sani- 
tarians regarded the environment as the main source of infection. We 
now know that water, soil, air, and food may be the vehicles by which 
the viruses of the communicable diseases are sometimes transferred — 
that is, they are media of conveyance rather than sources of infection. 
Most of the microorganisms causing the communicable diseases of man 
are frail and soon die in our environment, as in the air, soil, or water. 
Most of them are obligate pathogens and cannot or do not grow or 
multiply in our environment. 

From the lower animals, particularly the domesticated animals, man 
contracts a number of infections. Thus we contract rabies from the 
dog; plague from the rat; glanders from the horse; trichinosis from 
hogs ; anthrax from cattle ; malta fever from goats ; foot-and-mouth dis- 
ease from cattle; tuberculosis, in part, from cattle; tapeworms and 
other animal parasites from the meat of fish, fowl, and mammals. Vari- 
ous skin parasites are also contracted from the lower animals, as ring- 



worm from cats, fleas from dogs, etc. The number of these diseases 
and the extent of their ravages are notably less than those contracted 
from man himself. 

The knowledge that most infections are spread rather directly from 
man to man brings in all the forces of sociology to that of preventive 
medicine. The task of preventive medicine is thereby rendered much 
more difficult from the fact that most infections depend upon the con- 
trol of man himself. We ruthlessly wage war against insects or against 
infected food or water. In other words, we can arbitrarily control our 
environment to a very great extent, but the control of man himself 
requires the consent of the governed. Thus it is easier to stamp out 
yellow fever than to control typhoid fever. Tt is easier to suppress 
malaria than tuberculosis, rabies than influenza, trichinosis than measles. 
Cattle appear to be mutely thankful when protected by inoculation 
against blackleg or anthrax, but man rebels against one of the best 
of all specifics — vaccination against smallpox. The fact that man is 
the chief source and reservoir of most of his own infections adds greatly 
to the scope and difficulties of public health work and often makes the 
prevention of disease depend upon social changes. In this sense pre- 
ventive medicine is the true sociology. 

Modes of Transference. — The viruses of the communicable diseases 
may take various routes of transference from man to man or from 
animal to man. These routes are spoken of as the modes of infection, 
the modes of transference, or sometimes as the vehicles of infection. 
Formerly they were spoken of as the "channels of infection," but now 
we restrict that term to the special channels by which the infection 
enters the body. Thus the channel of infection in tuberculosis may be 
the respiratory tract, the digestive system, or the skin; whereas the 
mode of infection is from tuberculous sputum, either by direct contact 
or through the air. as in droplet infection, or through milk or some 
other vehicle. 

The modes of transference may be grouped, for convenience, under 
three general heads: (1) direct, (2) indirect, and (3) through an in- 
terrnediate host. In the great majority of cases the virus is transferred 
more or less directly by what is now known as contact infection. In 
many instances the virus is transferred indirectly through water, food, 
soil, air, etc. In a large group of diseases the transfer is through an 
intermediate host which furnishes the growing list of insect-borne dis- 

CoxTACT Infection. — "Contact infection" is a convenient term in- 
tended to include a group of circumstances in which infection is spread 
more or less directly or indirectly from person to person. Contact in- 
fection assumes a transfer of quite fresh infective material. Actual 
contact between the two individuals is not necessary, but the convey- 


ance is, nevertheless, pretty close in time and space. Contact infection 
alone may be responsible for epidemic outbreaks, even in the case of 
typhoid fever. 

The diseases in which contact infection plays a dominant role are 
those in which the virus leaves the body in the discharges from the 
mouth and nose, as tuberculosis, diphtheria, scarlet fever, measles, in- 
fluenza, common colds, cerebrospinal meningitis, whooping-cough, 
mumps, etc. Contact infection also pays a large role in diseases in which 
the virus leaves the body in the fecal and urinary discharges, as in 
typhoid, cholera, dysenter}^, and other intestinal infections. 

In contact infection the virus may be transferred from man to man 
directly by actual contact, as in kissing, or more indirectly upon soiled 
hands, contaminated towels, or infected cups, spoons, toys, remnants 
of food, and other objects which have recently been mouthed or handled 
by the infected person. As a matter of fact, the ways by which the 
infection may be transferred, and still be considered contact infection, 
are numerous and varied. In every instance, however, the transfer is 
brought about in pretty close association with the infected person. 

IxDiEECT IxFECTiox. — A large group of diseases are conve^-ed in- 
directly from persoq to person through the water, food, soil, and occa- 
sionally through the air. Diseases may be conveyed great distances 
by means of food or water; they are never conveyed long distances 
through the air. In the large majority of the diseases contracted by 
indirect infection the virus is taken into the system through the mouth 
and discharged from the body in the feces. The best examples of 
this class are typhoid fever, cholera, and dysentery. The relation of 
soil, food, water, air, and our environment is discussed separately. 

The insect-borne diseases form a large and important group, which 
are fully discussed on pages 181 to 271. 

Carriers. — By the term "carrier" we understand a person who is 
harboring a pathogenic microorganism, but who, nevertheless, shows no 
signs or symptoms of the disease. Thus a person may have diphtheria 
bacilli in the nose and throat, but, nevertheless, be in good health. 
The same is true with the pneumococcus, the meningococcus, strepto- 
coccus, and many other microorganisms. Persons may have typhoid 
bacilli, cholera vibrio, or hookworm in their intestinal tract without 
showing manifestations of these parasites. Furthermore, persons may 
have Plasmodia in their blood or spleen without having clinical malaria, 
and so on through a long list of infections. 

Persons who harbor pathogenic bacteria without showing symptoms 
are known as "'bacillus carriers," those who harbor protozoa are known 
as "protozoon carriers,"' etc. Carriers may be acute, chronic, or "tem- 
porary" — that is, a person who discharges pathogenic microorganisms 
a few weeks after convalescence is known as an "acute carrier," one who 


continues to harbor the microorganism for months and years is known 
as a "chronic carrier." A "temporary carrier" is a person in good 
liealth who has never had (lie infection, l)ut who harbors and discharges 
a patliogenic microorganism for a brief sjjace of time. 

The demonstration that many persons are carriers of infection lias 
thrown a new light upon the control of the communicable diseases. 
With the new facts has come a realization of added difficulties. Carriers 
can only be detected by painstaking laboratory examinations. When 
discovered their control is as difficult as it is important. We cannot 
lightly imprison persons in good health, even though they are a menace 
to others, especially in the case of bread winners. In some infections 
there are so many carriers that it would require military rule to carry 
out such a plan. Fortunately in most cases absolute quarantine is not 
necessary. Sanitary isolation is sufficient. Thus the danger from a 
typhoid carrier may be neutralized if the person exercises scrupulous 
and intelligent cleanliness, and is not allowed to handle food intended 
for others. Such a person might well be engaged as carpenter, seam- 
stress, or other occupation without endangering his fellowmen. 

The fact that carriers exist in a large number of diseases makes 
their suppression one of great practical difficulty. The cure of carriers 
is one of the pressing problems in preventive medicine. One hopeful 
feature of the carrier situation is that their number may be diminished 
by isolating and diminishing the cases of the corresponding disease. 
Thus, the number of typhoid carriers falls off sharply as a result of any 
successful measure directed only against the clinical case. The facts con- 
cerning carriers have been discussed separately under each disease in 
which they occur. 

Missed Cases. — By missed cases we understand mild and atypical 
instances of disease which are not recognized clinically. Almost all 
diseases vary greatly in severity. Thus we have walking typhoid and 
ambulant plague. Measles, scarlet fever, yellow fever, influenza, and 
most other infections may be so mild that they escape notice. Even the 
patient himself may not know he is sick. These mild cases go to school, 
ride in street cars, attend theaters, continue at their usual work in 
crowded factories and other places, handle our food, and thus spread 
infection. It is now well known that missed cases are a prolific source 
of spreading the infection of many of the communicable diseases; they 
form an important factor in preventive medicine. 

Channels of Infection. — There are numerous channels by which in- 
fection may enter the body. These are usually grouped under three 
headings: (1) the respiratory tract, (2) the digestive tract, and (3) 
through the skin. Perhaps 90 per cent, of all infections are taken into 
the body through the mouth. They reach the mouth in water, food, 
fingers, dust, and upon the innumerable objects that are sometimes 


placed in the mouth. The fact that the great majority of infections 
are taken by way of the mouth gives scientific direction to personal 
hygiene. Sanitary habits demand that the hands should be washed 
before eating, and fingers should be kept away from the mouth and 
nose, and that no unnecessary objects should be mouthed. All food 
and drink should be clean or thoroughly cooked. These simple pre- 
cautions alone would prevent many a case of infection. 

"Contagious" and "Infectious." — These are popular terms which 
lack scientific precision. The words have been used in very diverse 
senses. A contagions disease is one that is readily communicable — - 
in common parlance, "catching." Formerly a contagious disease was 
considered as one which is caught from another by contact, by the 
breath, or by effluvia. If contagious diseases are limited to those con- 
tracted by direct contact or touch, as the etymology of the word signifies, 
only syphilis and diseases similarly contracted would be contagious. 
As a matter of fact, smallpox and measles are types of contagious 
diseases, as the term is now usually understood. 

An infectious disease is usually considered as one not conveyed 
directly and obviously, as in the case of contagion, but indirectly through 
some hidden influence or medium. In the days when specific febrile 
diseases Avere regarded as caused by miasmata and noxious effluvia, the 
terms "infectious" and "miasmatic" diseases were more or less synony- 
mous. Typhoid fever was often taken as a type of an infectious disease. 
Malaria was the type of a miasmatic disease. 

These distinctions are entirely artificial, and serve no useful pur- 
pose. Most of the communicable diseases may be transmitted from the 
sick to the sound in several ways. Dividing diseases into those which 
are contagious and those which are infectious entirely leaves out of 
consideration the important class of insect-borne diseases. The terms 
contagious and infectious have always lacked scientific precision and 
have been the source of some confusion. The word "communicable" 
is a much better term and should be given preference. 

A communicable disease is one caused by a specific virus transferred 
from person to person, or from animal to animal, in a great variety of 
ways. The term "communicable" ignores the mode of transference. 
There is a great difference in the degree of communicability ; some 
diseases are readily communicable, others transmitted with difficulty. 
The evidences of communicability are not so obvious in chronic infec- 
tions, such as tuberculosis, or in diseases with a long period of incuba- 
tion, such as typhoid fever. The relationship between one case and the 
next is often far removed in time and space. If tuberculosis were an 
acute infection like diphtheria it would be regarded popularly as being 
just as contagious as that disease. 

Epidemic, Endemic, Pandemic, and Prosodemic. — A disease is said 


to be epidemic (epi=in, and demos:=people) when it is common to 
or affecting at the same time a large number of persons in a commu- 
nity. A disease which spreads rapidly and attacks many people at the 
same time is usually said to be epidemic. 

A disease is said to be endemic (em^iii. demos=people) when it 
is peculiar to a district or particular locality, or limited to a class of 
persons. An endemic disease is one which is constantly present to a 
greater or less degree in any place, as distinguished from an epidemic 
disease, which prevails widely at some one time or periodically. A 
sporadic (occurring singly) disease is one in which a lew scattering 
cases occur now and then. 

Endemic diseases are apt to flare up and become epidemic. In- 
sect-borne diseases are the best examples of endemicity, as their preva- 
lence is strictly limited by the geographic distribution of the intennedi- 
ate host. Yellow fever has long been endemic in Havana, cholera in 
India, typhoid fever in Washington, and plague in Tibet. 

These terms not only lack precision, but are variously conceived 
and differently defined. Thus typhoid fever is said to prevail in Bos- 
ton, but a similar number of cases in Germany would be regarded as 
an epidemic. For the purposes of maritime quarantine a disease is 
considered epidemic if there is more than one focus of infection ; that is, 
if several cases occur which have no apparent connection with each 
other. Strictly, therefore, according to this definition, two cases may 
constitute an official epidemic and the port would, therefore, be regarded 
as infected. 

It is not feasible to state just how many cases of a disease constitute 
an epidemic. Ordinarily a few cases of a communicable disease in a 
village or small town is not regarded as an epidemic; however, five 
cases of typhoid fever in Podunk (population 1,000) is the equivalent 
of 5,000 cases in a city of 1,000,000. By the same token, one or two 
cases in a small village would proportionately constitute an epidemic 
of unknown magnitude in a metropolis. 

"Pandemic" (pan=rall, demos:=people) is a term used to describe 
a disease which is more or less epidemic everywhere. Pandemics affect 
a large number of people in a large number of countries at the same time. 
Thus there have been four great pandemics of plague, when it spread 
to the four quarters of the globe. In 1889-90 influenza was pandemic. 
It is not usual, although quite proper, to regard tuberculosis and typhoid 
fever as pandemic. 

Sedgwick proposes the term " prosodemic" (proso=through, demos=: 
people) to take the place of the unsatisfactory word "endemic."' Proso- 
demic suggests the prevalence of a disease which is being communicated 
from person to person through the community by various means, but 
especially by contact. 


The Management of an Epidemic Campaign. — The first essential 
for success in the suppression of an epidemic is a knowledge of the 
epidemiolog}^ of the disease. The most important single information 
from a practical standpoint is a knowledge of the mode of transference 
of the infection. We do not know the cause of yellow fever; however, 
}-ellow fever campaigns have been crowned with success because we 
know it is transmitted through the bite of a mosquito. We know 
the cause of cerebrospinal meningitis, but there is still uncertainty 
concerning its usual mode of transmission, and, therefore, our efforts 
against this disease have been unavailing. The fact that we know that 
hookworm disease is transmitted by the larvge through the skin is of 
vital importance for the control of this disease. Without this knowl- 
edge at least 90 per cent, of our efforts to repress hookworm disease 
would be wasted. Wlien typhoid fever was regarded as chiefly a water- 
borne infection only partial success was achieved, because contacts, 
milk, flies, and other modes of transference of the typhoid bacillus 
were disregarded. 

In case the disease has an intermediate host or the virus is trans- 
ferred by an insect or other animal, a knowledge of the biology of the 
animal in question is of prime importance. For example, the habits 
and habitat of the yellow fever mosquito are quite different from that 
of the malarial mosquito. A campaign against the rat and flea without 
an acquaintance with their breeding and feeding places and the best 
means available to repress or suppress such vermin would be unsuc- 
cessful. The same is true in our campaign against tuberculosis with 
reference to cattle and man; in rabies with reference to dogs and other 
mammals; in sleeping sickness with reference to the tsetse fly; in 
Texas fever with reference to the tick; malta fever with reference to 
the goat; relapsing fever to the bedbug, and typhus fever with refer- 
ence to the louse. 

Authority. — Proper authority is necessary in order to enforce the 
necessary measures. This authority may come from the municipality, 
the state, or the federal government. In localized outbreaks, municipal 
authority is sometimes sufficient. More frequently the wider authority 
of the state is desirable. In our country it is a recognized principle in 
law that health laws and regulations belong to the police powers of the 
individual states. In most instances the general authority of the gov- 
ernment must be had, especially as interstate problems are almost al- 
ways involved in all epidemic outbreaks. The federal authority is lim- 
ited in health matters by the constitution. It therefore cannot act 
within a state unless invited to do so by the duW constituted authori- 
ties of the state. To send government health officers into a state against 
the will of the state corresponds to th.e sending of the regular army 
into a state to enforce measures against the will of the governor of 


that state. Such extreme measures are, tlierefore, only taken in times 
of emergency. Occasionally a state, refusing to take necessary action 
and protect the other states, is (|iiarantined. Thus, when California 
refused to officially recognize the existence of plague in 1899, the 
government quarantined the entire state. On account of our 
dual form of government it is important that the federal govern- 
ment, the state, and the local authorities cooperate in a friendly 
spirit. Epidemic diseases recognize no geographical houndary, and 
energetic and cooperative action is usually called for to suppress an 

It is the common experience of tiiose wlio have to deal with epi- 
demics that there is usually insufficient authority in law to provide for 
an emergency. It is, therefore, often necessary to take tlie bit in the 
teeth and adopt arbitrary measures which usually have the support of 
the better element in the community. Advantage may be taken of an 
epidemic to obtain laws to improve the health organization or the powers 
of the health officer. In this way an epidemic serves a useful purpose 
in arousing action. 

In the conduct of an epidemic it is very important that all the 
authority should center in one person. To conduct an epidemic with a 
board of health or a health committee or a commission of any kind in- 
vites failure. It would be just as foolish to have a board of generals to . 
fight a battle. Those who have been through many epidemics realize 
that it is no figure of speech to compare an epidemic campaign to a 
battle. It is a fight carried on at high tension, and, although the foe 
is invisible, it is a battle in every sense of the word. 

Ways and Means. — It is impossible to carry on a successful cam- 
paign against an epidemic without material resources. An epidemic 
campaign is expensive and success depends upon generous support. In 
most of the campaigns against yellow fever, plague, and cholera that 
have been waged in this country the expense has been borne in part 
by the government, in part by the municipality or state, and in part 
by subscriptions from citizens. The government has an epidemic fund 
appropriated by Congress and which is usually kept at about a million 
dollars. This fund is available only for plague, yellow fever, and 

Organization. — Headquarters should be organized at a convenient 
part of the city or the infected area, and headquarters should have all 
the modern office equipment and transportation facilities necessary for 
the quick dispatch of business. The city is then divided into sanitary 
districts. These may correspond to the political wards or the police 
districts and a subordinate is placed in charge of the work in each 
district. These districts are known as divisions, and the officer in charge 
of each division must establish headquarters for the work of that divi- 


sion. The actual work is done from division headquarters, under the 
direction of the chief in charge of the epidemic. 

It is also necessary to establish a laboratory in case laboratory diag- 
nosis is necessary for the recognition of cases or carriers, and emergency 
hospitals and detention barracks must be provided. Few cities have suf- 
ficient hospital facilities to meet a sudden emergency. Temporary ar- 
rangements must therefore be made. A modern school building makes 
a very good hospital and may be equipped for the reception of patients 
at short notice. Various squads must now be organized to carry on 
the particular work at hand. In the case of yellow fever these will 
be mosquito brigades; in the case of plague, rat brigades and disin- 
fectors, and in the case of smallpox, vaccinators, etc. 

It is frequently desirable, in fact often necessary, to make a house 
to house inspection throughout the infected district in order to collect 
certain data, to determine whether cases are being reported or hidden, 
and to carry out special measures. These house to house canvasses are 
under the immediate direction of the oificer in charge of the sanitary 
district and should be repeated as often as the occasion may demand. 

■ It is essential that all cases or suspected cases of the disease be 
promptly reported, for a case of communicable disease known is a case 
neutralized. It is the missed cases and the hidden cases that are par- 
ticularly dangerous. 

Education. — A campaign of education should be carried on at the 
same time that the disease is being attacked. The people are keenly 
alive and hungry for information. Well-worded articles in the news- 
papers, circulars, pamphlets, lectures, demonstrations, and the other 
usual methods are available. The education of the community is im- 
portant in order to obtain cooperation, for it is a handicap to fight 
an epidemic without the active support of the people. While the 
first duty of the officer in charge is to allay panic and calm the uuT'ca- 
sonable fears of the stricken community, the opposite extreme must be 
avoided. A healthy fear of the disease is one of the best instruments 
in the armamentarium of the sanitarian. It is almost hopeless to make 
progress against disease where the peojole supinely accept the conditions. 
Thus, if the people of the United States feared typhoid fever as they 
do yellow fever, it would soon diminish to the vanishing point. 


The word "quarantine" is derived from the Italian word "quarante," 
meaning forty. Its present-day meaning dates from the middle ages 
when Venice and other Hanseatic cities detained arriving ships with 
cases of pestilence aboard for a period of forty days. This was the first 
systematic application of maritime quarantine, although from the 
earliest times lepers were segregated or quarantined. To-day we have 


many kinds of quarantine : maritime quarantine, interstate quarantine, 
house quarantine, cattle quarantine, yellow fever quarantine, shotgun 
quarantine, etc. 

The dominating principle in modern quarantine is that it must be 
a sieve or filter and not a dam. All quarantines based upon the prin- 
ciple of the Chinese wall are doomed to fail. The object of quaran- 
tine is, then, to destroy, detain, or isolate infection with the least pos- 
sible hindrance to trade and travel. The art consists in regulating the 
openings in the quarantine sieve so as to hold back certain infections, 
but permit all else to pass. Maritime quarantine may be regarded as 
a coast defense against exotic pestilence, a defense which guards against 
an invisible foe ofttimes more damaging than hostile armies and navies. 
The cure for quarantine is sanitation. 

If all communities, especially seaports, were to place their cities in 
the best sanitary condition in accordance with the teachings of modern 
science, there would be little danger of disease spreading to epidemic 
proportions and very little need of maritime quarantine. If the ports 
in our southern littoral would fi'ee themselves of the Stegomyia mosquito 
they could laugh at yellow fever. A city containing few rats could not 
have an epidemic of plague. A port supplied. with a pure, well-pro- 
tected water supply need not fear a water-borne epidemic of cliolera. 
A thoroughly vaccinated community runs no hazard from snuillpox. 
Typhus fever could not spread in a community with cleanly personal 
habits, that is, one free from lice and other vermin. 

Maritime Quarantine. — Maritime quarantine in this country is en- 
forced only against six diseases, viz., cholera, yellow fever, plague, 
typhus fever, smallpox, and leprosy. We do not quarantine against 
typhoid fever, tuberculosis, measles, and other infections which are not 
greatly feared and which are constantly with us. Infections of a non- 
quarantinable nature, such as scarlet fever, measles, etc., arriving at a 
port are permitted to enter, but must then comply with the local laws 
and regulations. 

The period of detention is based upon the usual period of incubation 
for each disease and is as follows: 

Cholera 5 days. 

Yellow fever 5, sometimes 6 days. 

Plague 7 days. 

Typhus fever 12 days. 

Smallpox 14 days. 

Leprosy not admitted. 

The time of detention is usually counted from the completion of 
disinfection or at least from the last possible exposure to the infection. 
This is usually not a very difficult matter for the quarantine officer to 
decide, but in case of doubt the public is given the benefit. 


Ko communication is permitted with a vessel in quarantine except- 
ing under supervision of the quarantine officer; that is, no one is al- 
lowed to board the vessel or leave it, and nothing is allowed to be thrown 
overboard, taken ashore, or brought on board without the express per- 
mission of the quarantine officer. These restrictions apply alike to 
foods and to merchandise of all kinds. 

The vessel itself may be disinfected and furnished with a fresh 
crew and released from quarantine while the passengers and crew are 
detained in suitable barracks. Vessels trading with infected ports 
should carry immune crews; that is, persons who have either had the 
disease or have been rendered actively immune through one of the vac- 
cines or viruses. 

When a quarantinable disease breaks out on board a vessel it is of 
practical importance for the quarantine officer to determine whether 
the infection was contracted on board the vessel or on land. In the 
first case the vessel must be regarded as infected and the measures used 
for its purification are much more exacting than in the second case. 
Thus, if plague breaks out within five days from the time a vessel leaves 
an infected port, and no other case occurs, it is exceedingly probable 
that the patient contracted his disease ashore and was in the period of 
incubation when he came on board. If, however, |)lague breaks out after 
five days, and especially if secondary cases occur, it is evident that the 
ship itself is infected. The same reasoning applies to 3^ellow fever and 
the other communicable diseases. 

The measures taken at quarantine to keep out these diseases depend 
upon an accurate knowledge of their cause and mode of transmission. 
Briefly summarized, the measures applicable in each case are as follows: 

CJiolera. — Cases are removed from the vessel and isolated and that 
part of the vessel and the objects exposed are disinfected — formalde- 
hyde for cabins, sulphur dioxid for the hold, bichlorid solution for sur- 
faces, steam for fabrics and clothing. A search is made for bacillus 
carriers and a bacteriological examination is made of all cases of diar- 
rhea. Special attention is given to the water supply, food, and flies. 
After the sick are isolated the remainder are segregated in small groups. 
Those especially exposed are first bathed and their body clothing disin- 
fected before they are sent to the detention barracks. In case of cholera 
arrangements should be perfected for the disinfection of the dejecta. 
Baggage which has been exposed is disinfected by an approjoriate 
method, but as there is little danger in the cargo, especially if it con- 
sist of new manufactured merchandise, this may be passed without spe- 
cial treatment. 

If a vessel has taken water ballast at an infected port it is required 
to empty the same at sea and replace the presumably infected water 
with sea water. If this has been neglected the vessel must return to 


sea past the three-mile limit for this purpose. The water and the water 
tanks may be rendered safe by the use of chlorinated lime. 

The period of detention in the case of cholera is five days. 

Smallpox. — Ordinarily those who have had smallpox or who have 
had a recent successful vaccination are not detained. All others must 
submit to vaccination. Persons declining vaccination are detained for 
the full jjcriod of 14 days before they are released. As a rule, it is not 
necessary to detain cabin passengers because there is smallpox in the 
steerage, or to detain the firemen because there is smallpox among the 
stewards. Vessels arriving with smallpox on board on which the cases 
have been properly, isolated, personnel vaccinated, and other sufficient 
precautions taken to prevent the spread of the disease, need not be quar- 
antined further than the removal of the sick, the disinfection of com- 
partments, baggage, and objects that have been exposed to the liability 
of infection. 

Plague. — Passengers and crew from plague-infected ports are care- 
fully inspected at quarantine. The temperature of each person should 
be taken and it is desirable to make special examinations for bubos. 
A careful search is made for cases of Pestis minor, and the pneumonic 
form of the disease must also be kept in mind. The period of detention 
in the case of plague is 7 days. The sick are isolated in the hospital 
and the remainder segregated in small groups. All persons exposed 
to the infection are bathed and their body clothing disinfected. 

Rats and fleas on the vessel must be killed and burned. Usually 
sulphur dioxid is used ; sometimes hydrocyanic acid gas or carbon 

Special precautions must be taken to prevent the escape of rats. 
Vessels quarantined on account of plague should be anchored at suffi- 
cient distances from shore to discourage rats swimming to the land. 
If the vessel ties up to the dock, the hawsers must be guarded with 
inverted cones or balls of tar in order to stop rats reaching the ghore 
along these lines. Gangplanks must be taken in before dark, and, as 
rats are nocturnal in their habits, a searchlight will help to deter them 
from leaving the sliip. Nothing should be thrown overboard, not even 
deck sweepings; these should be burned, but not in the galley. 

A plague-infected ship is given a simultaneous disinfection with 
sulphur and the cargo is removed by a special procedure. After sul- 
phuring, the cargo is removed piece by piece to lighters, each article 
being examined as it swings overboard for rat nests. This work goes 
on during the day, while the empty cargo spaces are fumigated with 
sulphur during the night in preparation for the next day's unloading. 

Special precautions must also be taken at foreign plague ports to 
prevent the ingress of rats and also to prevent unnecessary human com- 
munication with infected areas. All vessels trading regularly with 



plague ports should carry an approved type of sulphur furnace^ such 
as the Clayton apparatus, to use during the voyage, in order to kill 
rats that may be on board. Such vessels should have an immune crew; 
that is, persons who have either had the disease or have been protected 
with Haffkine's prophylactic. 



Fig. 47. — A Device for Preventing Rats Traveling along Hawsers. 

Yellow Fever. — Vessels arriving at an infectible port from an in- 
fected port are fumigated and detained five da3's as a precautionary 
measure during the yellow fever season, even though there is no evi- 
dence of sickness on board. The yellow fever season usually extends 
from May 1 until October 1. The infectible ports are those situated 
upon the Atlantic seacoast south of the Chesapeake and those on the 
Gulf of Mexico. 

Five days covers the period of incubation of most cases of yellow 


fever and is sufficient as a precautionary measure, but in special in- 
stances, as, for example, if a case of yellow fever has occurred on board 
the vessel, then the detention is six days following fumigation. The 
sick are isolated by the use of mosquito screens. Patients with yellow 
fever should not be moved if this involves exertion or excitement, which 
may aggravate the disease. 

The vessel is fumigated with an insecticidal substance, preferably 
SOo, in order to kill the Stegomyia calopus. A search is made for 
breeding places, such as water casks, fire buckets, and other collections 
of fresh water where the Stegomyia larvae and pupae may develop. The 
disinfection of baggage and fomites is no longer practiced in the case 
of yellow fever. Experience has shown that wooden vessels are more 
apt to convey yellow fever than iron vessels. This is because wooden 
vessels carry water casks, which are the favorite breeding places for 
the mosquito, while iron vessels store their drinking water in tight 
compartments deep in the hold, inaccessible to mosquitoes. Vessels 
plying between infected and infectible ports should carry immune crews. 

Typhus Fever. — The period of detention for typhus fever is 12 days. 
If a case of typhus fever occurs upon a vessel and has been properly 
isolated, and the vessel is in good sanitary condition, there is practi- 
cally no danger of its spread, the case may be removed, disinfection 
practiced (insecticides), and the vessel, passengers, and crew permitted 
to proceed. But, if the case has not been isolated, or if the disease has 
spread from one person to another upon the vessel, or if the ship is in- 
fested with vermin and is otherwise in an unsanitary condition, those 
exposed are detained in quarantine until the period of incubation has 
elapsed. Quarantine procedures in the case of typhus fever are now 
focused entirely upon the louse, which is the carrier of the infection. 

Leprosy. — An alien leper is not allowed to land. The law requires 
the vessel on which he arrives to take him back again. It is unconstitu- 
tional to forbid the landing of an American leper, but as soon as he 
lands he comes under the laws of the city or state in which he finds 
himself. x4.1ien lepers are detained at the quarantine station and placed 
aboard again wlien the vessel is outward bound. 

Quarantine Procedures. — All vessels arriving at any port in the 
United States from a foreign port are considered to be in quarantine 
until they are given free practique. The practique is a certificate 
signed by the quarantine officer to the effect that the vessel and all on 
board are free from quarantinable disease, or the danger of conveying 
the same. In other words, free practique is a permit issued by the 
quarantine officer which the master of the vessel must present to the 
collector of the port in order that his vessel may be admitted to entry. 

Vessels in quarantine are required to fly a yellow flag (letter "Q" 
of the International Code) from the foremast. The quarantine officer 


boards the vessel usually upon the starboard side and examines the 
bill of health, the ship itself, the passengers, the crew, as well as the 
manifests of cargo, and sometimes the food and water supplies, etc. 
Vessels arriving after sundown must wait until sunrise for this inspec- 
tion; the time and details, however, vary greatly and depend upon cir- 
cumstances. Thus, at the port of Boston, there is no more need to ex- 
amine vessels bringing residents of London or Paris than there would 
be to examine a trainload of passengers from New York. 

The detection of infection on board a vessel requires knowledge, 
tact, and sometimes a detective instinct on the part of the quarantine 
officer. Where one of the communicable diseases is suspected the tem- 
perature of every person on board should be taken. Sometimes special 
examinations, as for bubos in the case of plague, are necessary. As a 
rule, all hands are mustered at a designated place on board the ship 
and then passed in review, one by one, before the examining physician; 
the number of persons are counted and compared with the ship's papers ; 
each person is critically scrutinized for evidence of disease, and suspects 
are placed aside for more careful examination later. The clinical 
records of the ship's surgeon are inspected with special reference to the 
diagnosis of those who have received medical care during the voyage. 
The manifest of cargo is examined for second-hand goods, upholstered 
furniture, bedding, hides, hair, or other objects that may require disin- 
fection. Finally, the ship itself is inspected, attention being given 
especially to the forecastle, steerage quarters, the galley, etc. 

The Bill of Health.— The United States Bill of Health is a docu- 
ment issued by our consul at the port of departure to the master of 
the vessel. The Bill of Health contains a complete description of the 
vessel, the number of officers, crew, and passengers (cabin and steer- 
age), its sanitary history, and the sources and wholesomeness of water, 
food supply, etc. Finally, it contains a statement giving the number 
of cases and deaths from yellow fever, cholera, smallpox, typhus fever, 
plague, and leprosy at the port of departure during the two weeks pre- 
ceding the departure of the vessel. The American Bill of Health, which 
is a formidable document, must be obtained by the master of the ves- 
sel in duplicate; one copy is destined for the collector of customs at 
the point of entry and the other for the quarantine officer. 

The Bill of Health is a consular document (State Department) at 
the port of departure, but becomes a customs paper (Treasury Depart- 
ment) at the port of entry. Vessels arriving at any port in the United 
States or its dependencies from a foreign port without this official Bill 
of Health in duplicate are subject to a fine of $5,000. Before the days 
of telegraphy the Bill of Health was an important document and often 
gave the quarantine officer the first information of pestilential disease 
abroad. The quarantine officer must now keep himself informed not 


only of tlie health conditions of the port of departure, but of the places 
from which the passengers and crew are recruited. 

There are many kinds of bills of health; each country has a form 
of its own. Formerly a bill of health was simply a statement that the 
port of departure was or was not free of pestilential disease; that is, 
the bill of health was either "'clean" or "foul."' The American Bill of 
Health gives much more valuable information in detail. The only bill 
of health that is of service to the vessel upon arrival is the American 
Bill of Health, although several bills of health may be issued to the 
vessel at the port of departure. Thus, a British vessel leaving the port 
of Rio de Janeiro takes three bills of health, one from the British con- 
sul, required by the British admiralty laws, another from the Brazilian 
authorities, which is a clearance paper, and the third from the Amer- 
ican consul, which is the only one of service upon reaching a port in 
the T'nitod States. 

The Equipment of a Quarantine Station. — The equipment of 
a quarantine station consists of boarding vessels, such as tugs, launches, 
and rowboats; of an inspection place where passengers, crew, and sus- 
pects may be examined (the facilities on board the ship are usually 
inadequate for this purpose) ; of disinfecting apparatus for the use of 
steam, sulphur dioxid, formaldehyde, and insecticides; shower baths; 
detention barracks for steerage, intermediate, and cabin passengers, as 
well as the crew of the vessel; isolation wards in which cases of the 
quarantinable diseases may be cared for, and special wards where sus- 
pects or non-contagious cases may receive treatment. A well-equipped 
quarantine station further needs dining-rooms and kitchens for the 
various groups detained; quarters for the cjuarantine officers and help; 
a wharf and boat house, and some provisions for recreation of those 
in quarantine to dispel the ennui of the isolation. Finally, a crema- 
tor}', a steam laundry, and special arrangements for the disposal of 
sewage and garbage are essential. 

A laboratory is an essential feature of a modern quarantine station. 
It is necessary in order to make diagnoses and to recognize bacillus 
carriers, etc. In other words, a quarantine station, on account of its 
importance and isolation, must be a well-equipped and self-supporting 

Qualifications of the Quarantine Officer. — The quarantine officer 
must be a good diagnostician. He should have a special acquaint- 
ance with the diseases against which he stands monitor. Further, he 
must be familiar with the modes of spread of the quarantinable dis- 
eases and must know the value and limitations of the germicidal agents 
and insecticides he uses. Finally, he must be familiar with matters 
nautical, and have an extensive knowledge of geography. It is the duty 
of the quarantine officer to keep posted as to the sanitary conditions 


of all countries, especially the towns and places having commerce with 
his port. 

Disinfection of Ships. — The disinfection of a vessel does not dif- 
fer materially from the disinfection of houses and rooms. It should 
not, however, be attempted by one not familiar with the intricacies 
of marine architecture and matters nautical, for many special condi- 
tions are met with on board ship that are very different from those 
found on shore. While the principles of disinfecting as applied to a 
vessel present nothing unusual, the application of these principles calls 
for much ingenuity and the keenest vigilance on the part of the dis- 

It is important to enlist the sympathies of those on board with the 
necessity of disinfection, for the successful accomplishment of the 
purification of the vessel may be materially helped by the cheerful 
cooperation of the passengers and crew; otherwise the difficulties of the 
problem are greatly magnified. 

Formerly a distinction was made between the methods of disinfect- 
ing a wooden and an iron vessel. This arose from the fact that almost 
all wooden vessels have some rotten and spongy wood, especially about 
the forefoot and bilge. There are also many more cracks and open 
joints about a wooden ship than a metal one which afford lodgment 
for organic matter. In addition to this, a wooden hull is always dam- 
per than an iron hull, for almost all wooden vessels leak more or less. 
It was formerly believed that the microorganisms of disease were apt 
to become deeply lodged in the moist dirt and organic matter of the 
many crevices, but we now know that this is largely theoretical. 

A vessel is rarely so badly infected that it needs a disinfection 
throughout. Just what portion of the vessel and its contents requires 
treatment is often a very difficult problem to solve. There is no more 
reason to fumigate the hold of a vessel because smallpox appeared in 
the cabin or steerage than there would be to disinfect the basement and 
subbasement of a tenement house because a case appeared in one of 
the upper stories of the building. When a communicable disease oc- 
curs on board a vessel the infection may be confined to one or two 
compartments or to a limited area quite as successfully as this may 
be done in buildings on shore. "In case of doubt, disinfect," is not 
a bad rule for the quarantine officer to follow in his practical deal- 
ings with ships. For, after all, the measures which must be taken are 
greatly in excess of the absolute requirements. 

Much may be learned by a thorough inspection of the vessel. To be 
sure, we cannot see the germs with our unaided vision, but we can see 
the dirt and moisture and other conditions which favor their life and 
virulence and can discover the feeding and breeding places for vermin. 

It is, therefore, the duty of the quarantine officer to require a very 


thorough mechanical cleansing of all parts of the ship which, in his 
judgment, require it. This matter is dwelt upon because filth and ver- 
min are conditions too frequently met with on tlie sea and one of great 
importance to communities and nations. 

Wliile the general methods of treating vessels are the same for most 
of the bacterial infections, special methods are called for with each dis- 
ease. For example, in cholera particular attention must be paid to the 
water and food supply; for plague the destruction of rats and fleas 
is of prime importance; for yellow fever attention must ])e directed 
against the mosquito; for smallpox vaccination and the usual disinfec- 
tion of the living apartments, clothing, bedding, and the like are re- 
quired, while for typhus fever the warfare must be waged against lice. 

The disinfection of a large vessel cannot effectively be done with- 
out all the modern contrivances of a well-equipped quarantine station. 
A rowboat and launch or a small sailing craft may be disinfected with 
a tub of bichlorid solution, but good work cannot be accomplished on 
a large vessel by the use of makeshifts. 

Before the disinfection of a vessel is commenced it should be brought 
alongside the pier or barge containing the necessary apparatus. All 
the passengers are then to be taken off and all the crew, only excepting 
the few who are necessary for the safety of the vessel and those who 
are to help in the disinfection. The quartermaster, the boatswain, and 
the carpenter are very useful hands to aid in the process on account of 
their practical knowledge of the individual peculiarities of the construc- 
tion of the vessel and their intelligence in carrying out directions with 

When the personnel have left the vessel all their effects are removed 
and disinfected, if necessary, in accordance with the methods outlined 
for objects of that class. Baggage, bedding, and other objects, no mat- 
ter what their character, after disinfection should not be returned on 
board until the treatment of the vessel itself is finished. This injunc- 
tion applies, of course, equally well to persons. In fact, no one should 
be allowed on the vessel except those actually engaged in the work, 
who, as far as practicable, should be immune and should wear suitable 
garments. All the bedding, bed clothing, hangings, floor runners, and 
other fabrics that have been exposed to infection must now be re- 
moved to the steam chamber. Especial care must be taken to obtain 
all the used and. soiled linen, which is usually kept in special compart- 
ments called the "dirty linen lockers," which are usually under the care 
of one of the stewards. For some reason there is a dislike to disclose 
the presence of this soiled wash to the quarantine officer. 

After all the objects needing disinfection by special process have 
been removed, attention is then directed to the vessel itself. The vari- 
ous compartments of the vessel may be disinfected by any one of the 


methods described under Eoom Disinfection, formaldehyde being the 
choice of the gases and bichlorid of mercury (1-1,000) being the most 
suitable solution for the treatment of walls, floors, etc. 

The bichlorid solution, which is sometimes used for flushing the 
forecastle, the steerage compartments, and quarters for petty officers, 
etc., may be applied with a force-pump or by means of mops and buck- 
ets. In applying the disinfection solution with a hose begin at one end 
of the deck ceiling and systematically flood every inch of surface, com- 
ing down the walls, and finally the floor. 

In disinfecting large vessels it is well to start forward with the 
forecastle and work aft systematically, first on the starboard, then on 
the port side, taking care to require every door to be unlocked and 
trusting only to a personal inspection concerning its contents and uses. 
There are certain places, such as the lamp-room, the paint locker, the 
sail locker, the chain locker, the carpenter shop, and chart room, the 
pilot house, the engine and boiler rooms, and the machinery, that are 
rarely infected, and, as a rule, need no treatment. Special care, how- 
ever, must be given to the sick bay and any apartment in which a pa- 
tient was cared for, and all living apartments, including the steerage. 

The water closets on board ship should be thoroughly cleansed and 
flushed with water and may be disinfected with chlorinated lime or 
carbolic acid. They may also be hosed with the bichlorid solution 
while that is being applied. In sailing vessels of the older type the 
forepeak needs similar treatment. 

The hold rarely needs treatment on account of bacterial infection. 
About the best way to disinfect the holds of vessels is by sulphur fumi- 
gation or by a solution of corrosive sublimate applied with a hose. 
The bilge may be flushed with carbolic solution or chlorinated lime and 
then pumped out. WTien the hold is fumigated with sulphur, this may 
be burned in iron pots set in pans of water. The pot should be placed 
in an elevated position either on piles of ballast or on the 'tween decks. 
In leading sulphur fumes into the holds from a sulphur furnace it is 
considered best to lead the pipes down the hatch-well toward the bottom 
of the hold, so that the apartment may fill up with the fumes from the 
bottom, displacing the air above. For this reason openings above for 
the escape of the air must be provided. This is best managed by leav- 
ing one or two of the ventilators open, or part of the hatch, and after 
the gas has begun to escape in some quantity to close up tight. 

The amount of sulphur to be burned may readily be computed from 
the tonnage of the vessel. A registered ton is 100 cubic feet. Count 
half a pound for each ton, which will make the necessary five pounds 
per 1,000 cubic feet. The gross tonnage of a vessel indicates her ac- 
tual cubic capacity. The net tonnage gives the capacity of her cargo- 
carrying space. The difference between the two will give the capacity 


of the spaces devoted to the engines, machinery, living apartments, 
storerooms, etc. In sailing vessels and in freighters the net tonnage 
may be taken as the cubic capacity of the hold. In estimating freight 
40 cubic feet of merchandise is considered a ton, provided the bulk 
does not weigh more than 2,000 pounds. This ton, used as a commer- 
cial unit for freight charges, must not be confused with the registered 
tonnage based upon the measurement of the vessel. 

In fumigating vessels for yellow fever, plague, and other insect- or 
animal-borne diseases, the fumigation should be simultaneous in all 
parts of the vessel. Following tliis, special rooms and apartments may 
be given individual treatment, depending upon circumstances. 

The empty compartments of an iron steamer may be disinfected by 
steam, provided it is above the water line. The compartments of such 
vessels usually have steam pipes for use in case of fire. Clothing and 
other fabrics may also be disinfected by steam, by exposing them in the 

The water tanks and casks of vessels sometimes need special treat- 
ment. The water may be infected with cholera, typhoid, dysentery, 
or other water-borne infection. The water may be disinfected in situ 
by the addition of chlorinated lime, using an amount sufficient to make 
a one per cent, solution. This should stand at least 24 hours before 
it is pumped out. 

Water casks onr sailing vessels are very apt to be breeding places for 
mosquitoes. These should be emptied and cleansed. The water con- 
taining the larvae may be spilled overboard, as neither the anopheles 
nor the stegomyia may develop in salt water, otherwise the larvae should 
first be destroyed. 

For the destruction and treatment of rats, etc., on vessels see pages 
245 and 252. 

Cargo. — As a rule, the cargo of a vessel infected with pestilential 
disease needs no disinfection. Individual articles of the cargo, such as 
rags, household goods, second-hand articles, or food products, from in- 
fected localities may need treatment. New articles of merchandise or 
new manufactured goods seldom carry infection. 

In the case of plague the cargo may need special treatment on ac- 
count of rats (see page 324). 

Ballast. — A'essels bring two kinds of ballast: (1) water, (2) solid. 
Solid ballast consists of the greatest variety of substances. The kind 
which is most objectionable from the standpoint of the health officer is 
called "sand" by the captain, but an inspection of this sand will dis- 
cover the fact that it often consists largely of street sweepings and rub- 
bish from the port from which the vessel hails. Such ballast should not 
be unloaded on the city front, especially if it comes from an infected 
district. Ballast consisting of clean, hard rock or sand from the beach 


is not apt to carry infection of any kind, and usually needs no attention 
from the quarantine officer. 

Modern vessels all use water ballast. The tanks may be filled from 
a river, fresh water lake, or other body where cholera, typhoid, or dysen- 
tery prevails. It is a rule in quarantine practice to require vessels in 
fresh water ballast from cholera-infected districts to return to the open 
sea, where the ballast tanks are pumped out and refilled with salt water, 
provided this has not been done on the high seas. Before the water is 
pumped out it should be treated with chlorinated lime. 

Foreign Inspection Service. — To aid the quarantine officer every 
American consul is required to report regularly certain facts concern- 
ing the presence and progress of epidemic diseases. Medical officers of 
the government are also stationed at various countries in order to su- 
pervise the sanitary condition of vessels, their cargo, and passengers 
leaving for the United States. This may be called preventive quaran- 
tine, for it is a distinct help in keeping out infection and facilitates 
trade and travel. Thus, in Italy, during the cholera times, an officer of 
the Public Health and Marine Hospital Service stationed at Naples suc- 
cessfully kept that disease off vessels sailing from Naples to the United 
States, whereas vessels sailing from Naples to other ports and without 
sanitary supervision carried cholera in several instances. 

National versus State ftnarantine.— All the maritime quarantines in 
this country are now controlled by the national government, except- 
ing the ports of Boston and New York. At Boston the maritime 
quarantine is in charge of the city health authorities, and at New York 
it is a state institution. At a few other ports a local quarantine is 
maintained in addition to the national service. The federal quarantine 
service is administered by the Public Health Service, a bureau in the 
Treasury Department. 

It is evident that maritime quarantine should be administered uni- 
formly so as not to prejudice or favor the commerce of a port. Not 
only is uniformity insured by a central service, but there is a decided 
gain in efficiency for obvious reasons. Maritime quarantine deals mainly 
with foreign shipping. The Constitution reserves for the federal gov- 
ernment the right of treating with foreign powers; from this point, 
therefore, maritime quarantine is mainly a function of the federal gov- 

Interstate Quarantine. — In accordance with our Constitution the 
federal government has limited power within the state, but has practi- 
cally unlimited authority to prevent the spread of infection from one 
state or territory, or the District of Columbia, to another state or terri- 
tory, or the District of Columbia. Interstate quarantine involves in- 
terstate travel and commerce; the pollution of streams flowing through 
more than one state; railroad and steamboat sanitation, and all sinailar 


questions. Congress has passed a comprehensive act. Section III of the 
Act of February 15, 1893, authorizing the Public Health and Marine 
Hospital Service to enforce interstate quarantines in the case of con- 
tagious and infectious diseases. The regulations, however, prepared 
under this act comprehend only the six quarantinable diseases, and have 
only occasionally been enforced in the case of yellow fever, cholera, or 
plague. There are no interstate regulations concerning typhoid fever, 
tuberculosis, measles, and other non-quarantinable diseases. It is evi- 
dent that this is one of the important phases in which government 
activity can accomplish especial good; for, while the government has 
limited power within the state, it has practically unlimited authority 
so far as interstate relations are concerned. Widespread diseases will 
never be adequately controlled by the local authorities without the co- 
operation of the government. It is evident that, if one state should rid 
itself of typhoid fever, measles, or tuberculosis, it would soon become 
reinfected from the neighboring states. Interstate sanitation is one of 
the burning questions needing vigorous action and cannot be adequately 
enforced without extending the scope and powers of the present federal 
health authorities. 


In theory isolation is the most perfect single method to check the 
spread of a communicable disease. The results in practice, however, 
have been somewhat disappointing on account of unusual difficulties. 
The statement has frequently been made, especially with reference to 
typhoid fever, that if all the cases could be isolated (which includes 
the disinfection of the discharges) we would soon see an' end of the 
infection. We now know that this statement is not true, on account 
of the bacillus carriers and the mild and unrecognized or "missed" 
cases. Because the isolation of the reported cases represents only a 
portion of all the foci of infection and, therefore, at best could not in 
itself control an epidemic disease, discredit has been thrown upon this 
procedure, which is one of the essential features of all systems of quar- 
antine. As a matter of fact, it has been shown that in certain diseases, 
like measles, which is communicable for three days or more before the 
nature of the disease is recognized, isolation has practically no influ- 
ence in diminishing the prevalence of this widespread infection. It is 
true ordinarily that a case of measles does most harm before it is 
isolated; nevertheless, this is no reason why it should be permitted to 
further endanger the community. The value of isolation is also dimin- 
ished by the prevalence of carriers. In fact, its practical usefulness in 
a given infection is inversely proportional to the number of carriers. 

If each case isolated prevents on the average only one other fresh 
infection, there would still be justification sufficient to continue th? 


practice. As a matter of fact, the practical value of isolation varies with 
each disease, depending upon the degree of its communicability, the 
time when it is communicable, the promptness by which it may be 
recognized, the modes by which it is transferred, the existence of latent 
infections, missed cases, carriers, and other factors which influence the 
spread of the infection. 

The degree of isolation varies markedly with the different infections. 
A case of yellow fever may be isolated under a mosquito screen, and a 
case of diphtheria or scarlet fever may be effectively isolated in a bed in a 
general ward, provided intelligent and painstaking care is exercised to 
destroy the infection as it leaves the body. Isolation of the more read- 
ily communicable diseases, as smallpox and measles, should be much 
more absolute. Typhoid bacillus carriers need not be imprisoned. It 
is sufficient to limit their activities, especially to prevent their occupation 
in kitchens, dairies, or about foodstuffs. There is no good reason to 
isolate a consumptive or leper without open lesions — that is, cases in 
which the bacilli are imprisoned in the tissues and not discharged into 
the environment. A careful consumptive or leper may be allowed a 
wide latitude. On the other hand, isolation in chronic infections, such 
as tuberculosis and leprosy, with open lesions is the most helpful and 
at the same time the most difficult single procedure we have to control 
their spread. The careless, indigent, ignorant, or helpless consumptive 
is a public menace that needs energetic and sometimes arbitrary iso- 

Isolation may most readily and effectively be carried out in hospitals 
or sanatoria. Proper isolation in the home requires a special room 
or rooms, intelligent nursing, appliances for disinfection, etc., a com- 
bination often difficult to arrange. House quarantine varies with the 
different diseases. To carry it out rigorously in all cases and under all 
conditions is folly. Different diseases need different procedures. Some- 
times it is sufficient simply to placard the house as a warning. At other 
times it may be necessary to station sanitary guards about the premises 
to enforce the quarantine. The imperfections of strict isolation by the 
"shutting in of houses" are graphically described in Defoe's "Journal of 
the Plague Year." 

Isolation camps or temporary barracks in times of epidemics are 
effective measures in checking the spread of some infections. This 
method has proved effective in actual practice in the case of smallpox, 
yellow fever, plague, cholera, and other diseases. 

It often becomes a difficult question to determine whether the well 
m^embers of a household should also be quarantined — especially whether 
the well children should be permitted to attend school. This perplex- 
ing question must be decided for each disease separately, and the deci- 
sion in each disease is sonietimes modified by attending factors. Usually 


the other children in the family in the case of scarlet fever are excluded 
from school for four weeks from the beginning of the last case. In 
most cities the same rule holds for diphtheria, although here we are 
able to determine whether the children are bacillus carriers or not. 
At least two negative cultures from the nose and throat should be re- 
quired before such children are allowed freely to mingle with other 
children. The principal factors which determine whether the well 
children in a family shall be permitted to attend school or not in any 
particular infection rest upon our knowledge as to whether the disease 
is conveyed by a third person and the frequency of bacillus carrying 
and missed cases. 

Isolation becomes one of our most valuable public health measures 
when communicable diseases affect persons working about milk, meat, 
and other foods capable of conveying infection. 

One of the practical objections to isolation and one reason that it 
meets with so much opposition from the public is that the compensa- 
tion of the wage earner ceases through no fault of his own. It is evi- 
dently unjust to practically imprison and thus seriously punish a mem- 
ber of the community, not for his own good but for the good of the 
community, because he or some member of his family has contracted 
an infection, perhaps through some fault of the community itself. It 
is, therefore, reasonable and just that wage earners and others should 
be compensated and their personal interests safeguarded during enforced 

Isolation only reduces to a moderate degree the prevalence of dis- 
ease. The limitations of this valuable procedure are now well under- 
stood. With improved methods of diagnosis and increased knowledge 
of the methods of spread of disease, isolation will be made increasingly 
effective. Every case isolated is a focus of infection neutralized. Al- 
though not. as satisfactory in practice as it is in theory, isolation will 
ever remain one of the chief administrative procedures for the control 
of the communicable diseases. 



Imnmnity or resistance to disease is the very foundation of pre- 
ventive medicine. It is the overshadowing factor in hygiene. In this 
sense we use the term "hygiene" to include the care of the person, in 
contradistinction to '■sanitation/' which deals with the environment. 
There is no sharp line of demarcation — we speak of hygiene of the 
teeth, of sleep, of bathing, of exercise, or food and drink, and of those 
conditions which are more or less intimately associated with the body; 
we speak of the sanitation of the home, of schools, of cities, of farms; 
sanitary science considers the air, soil, climate, and our surroundings 
as they affect health. Sanitation, then, is largely impersonal; hygiene 
is personal, and, as far as the prevention of disease is concerned, one of 
the most important factors in hygiene is immunity. 

The word "immunity" is a very old term — we still speak of immu- 
nity to crime,^ but it is only of late years that we are beginning to un- 
derstand the mechanism by which the body protects itself against in- 
fection. The advances have been so rapid that these studies may now 
be grouped into a separate science known as Immunology. 

Immunity is a function of all living beings (animals and plants), 
and in its widest form is one of the fundamental properties of life. 
Thus, as long as we are alive the colon bacillus in our intestinal tract 
and the spores of the hay bacillus on our skins do us no harm, but the 
moment we die, and ofttimes shortly before death,- these and other bac- 
teria invade our tissues and disintegrate them. 

Immunity may be defined as the power which certain living organ- 
isms possess of resisting infections. Immunity is the contrary condi- 
tion to susceptibility. Hyper susceptibility is a special state of an exag- 

^ We may speak of immunity "from" a disease, "to" a disease, and 
"against" a disease. 

^ Terminal infections. 



gerated power of reaction and will be discussed separately under anaphy- 
laxis or allergie. The word resistance lias practically tlie same sig- 
nification as immunity. The term "tolerance" is conimoiily used to 
describe a limited form of immunity usually acquired by the repeated 
use of alkaloids, alcohol, and other poisons of comparatively simple 
chemical structure. While a high degree of tolerance may be acquired 
to such substances, a true immunity in the sense in which the term is 
now used is never produced. In the case of tolerance, antibodies are 
not found in the blood. For the most part true immunity is produced 
against colloidal substances, while tolerance is largely limited to the 
crystalloids; this distinction, however, is not absolute. 

There are all gradations and various kinds of immunity. It varies 
in degree from the weakest appieciable amount to an almost absolute 
protection. It also varies greatly in duration — from the briefest period 
to a life span. Immunity, therefore, is a relative term. It may be 
natural or acquired, active or passive, local or general, pure or mixed, 
specific or general, family or racial, brief or lasting, strong or weak, 

Immunity is a function which is not limited to man and other mem- 
bers of the animal kingdom. It is common througliout the vegetable 
kingdom. ^Ye are indebted to Welch for the thought that the bacteria 
themselves also have this fundamental property of life. Thus, man is 
susceptible to the tubercle bacillus because the tubercle bacillus is im- 
mune to man; on the other hand, man is immune to the hay bacillus 
because the hay bacillus is susceptible to man. In this sense a micro- 
organism is called pathogenic or non-pathogenic, depending upon 
whether it harms or is favored by its host. This is the relation be- 
tween seed and soil. A fertile soil is susceptible; a barren soil is im- 
mune. The seed in the first instance may be pathogenic ; in the second 
non-pathogenic. The host is able to resist the intrusion and growth of 
the non-pathogenic microorganisms and protect itself against harm 
through its mechanism of immunity. If the protecting devices are in- 
sufficient to guard against attack, the germs multiply, produce poisonous 
substances, or harm the host in other ways. The reason that the same 
microorganism may be pathogenic for one host and harndess for another 
depends upon the presence or lack of immunity. The virulence of a 
microorganism is an expression of the intensity of the relation between 
the seed and the soil. Virulence may be strengthened or attenuated 
either b}^ increasing or decreasing the resistance of the host or by in- 
creasing or decreasing the resistance of tlie microbe. 

Mechanism of Immunity — Theories of Immunity. — It is now quite 
evident that the mechanism of immunity varies in different . infections 
and, to a certain extent, even in the same infection under different con- 
ditions. It must further be admitted that we are still in ignorance of 


the mechanism by which the body protects itself against many dis- 
eased states. 

Historically considered, immunology as a science dates back scarcely 
30 years. Many primitive people attempted to immunize themselves in 
a crude sort of way, but with methods now recognized as essentially 
sound. Thus, South African tribes tried to protect themselves against 
snake bites by using a mixture of snake venom and gum; the Moors 
immunized cattle to pleural pneumonia by placing some of the virus 
under the skin of the animal. The inoculation against smallpox used 
from time immemorial, and vaccination with cowpox introduced by 
Jenner in 1798, are examples of the first practical use of specific meth- 
ods in .the history of immunity. 

Pasteur was greatly influenced by Jenner's demonstration that a 
mild form of a disease protects against the severe form. Pasteur ex- 
panded the fact taught by Jenner into a general principle. Practically 
all of Pasteur's work in immunity that bore practical fruit, such as 
vaccinations against chicken cholera, anthrax, and rabies, is based upon 
this guiding principle. 

Pasteur in 1888 expounded his "exhaustion" theory, which was the 
first attempt at a scientific explanation of immunity. Pasteur was a 
chemist and his theory was a simple chemical conception, largely based 
upon his work upon the fermentation of sugar with yeasts. He re- 
garded the body immune because its food supply was used up and the 
microorganisms could, therefore, no longer grow — just as yeasts cease 
to grow when the sugar is used up in a culture medium. It is now 
easy to disprove, the exhaustion theory. Bacteria do not cease to grow 
on account of the exhaustion of the food supply, but rather on account 
of the production of products toxic to themselves. Further, bacteria 
may grow well enough in the dead tissues and fluids of immune animals, 
and, again, immunity may be induced by the inoculation of dead bac- 
terial products, substances which can hardly use up food material. Ee- 
cently Pasteur's exhaustion theory has been revived in a modified form 
by Ehrlich, who considers that there is sufficient evidence for this form 
of immunity in certain cases, as in cancer. Ehrlich calls it "atreptic" 

Chauveau proposed the "retenlion" theory, the exact opposite of the 
exhaustion theory. This theory is also based upon the analogy of the 
behavior of bacterial growth in vitro compared to their growth within 
the body. It soon became evident that bacterial growth ceases even 
though abundant food is present, and. that this inhibition is due to the 
retention of products of metabolism of bacterial activity. Chauveau 
considers that such substances are retained within the body, which thus 
protects it against further growth and development of the microorgan- 
isms and thus accounts for immunity. 


The above theories are generalizations which have now little more 
than historical interest. We now know that no one mechanism of im- 
munity will explain all cases. In some instances phagocytosis plays 
an important part; in others antibodies of various sorts; the side-chain 
theory appears to account for most of the facts in antitoxic immunity. 
In some cases the immunity is due to a negative property in that there 
is an absence of specific affinity between the poison and the cells. In 
others it is a positive factor and is due to the presence of substances 
able to neutralize the toxic action. The mechanism of immunity in 
some instances resides mainly in the blood and fluids; in other cases 
it is evidently more directly associated with cellular activity. In some 
instances immunity depends upon the power of immediate reaction in 
the sense of anaphylaxis. In all cases the mechanism is probably com- 
plex and multiple. 

The unsatisfactory state of our knowledge in certain fields of im- 
munity is well illustrated in the case of anthrax. The mechanism of 
protection is not at all understood in this infection, which was the first 
and classic illustration of a germ disease. The mechanism of immu- 
nity in common colds is also complex and obscure. 

Our resistance to disease is in many cases due to a simple mechani- 
cal or chemical protection against the invasion of the pathogenic micro- 
organisms; that is, the tissues are susceptible enough, but are guarded 
against the invasion of the germs of disease. Many examples may be 
cited in this category. Thus, one of the important functions of the 
skin consists in this mechanical protection of the tissues underneath. 
The smooth conjunctiva is protected by the constant washing of the 
tears and the motion of the eyelids. The lungs are safeguarded by the 
shape of the upper respiratory passages and the moisture of the mucous 
membranes, which act as a mechanical trap for many bacteria. Some 
of those that pass deeper are carried back by the mechanical action of 
the cilia. The sensitive and susceptible mucous membrane of the in- 
testines is partly protected through the acidity of the gastric juice, 
which is sufficient to destroy cholera vibrios and other microorganisms 
susceptible to acid. 

Within the body the mechanism of immunity is an adaptation of 
cell nutrition. The mechanism varies with different infections and in 
different stages of the same infection. In certain diseases the immu- 
nity seems to reside mainly in th^ activity of the cells. In other dis- 
eases the immunity is due chiefly to substances floating in the blood. 
The first is the cellular and the second the humoral theory. As we shall 
have occasion to see, the immune bodies in the blood are probably in 
all cases derived from the cells, so that the cells play the fundamental 
part in most cases of immunity. However, the great majority of the 
studies in immunology have been focused upon the changes in the blood. 


This is not due to the fact that the blood alone represents these changes, 
but that it best represents them, and thus affords the readiest method 
of attacking the problem. The blood is the most fluid and most cos- 
mopolitan of all the tissues of the body, visiting every part, bearing to 
each part certain substances, and removing from each part certain other 
substances. It is evident that it is easy to study the blood and its 
changes, as some of it may readily and repeatedly be withdrawn during 
life in order to observe its changes without in any wa}" harming the 
animal. The fundamental processes of immunity within the body must 
all depend upon some chemical change, but we know very little con- 
cerning the chemical composition of the substances that play the chief 
role or the chemical nature of the changes. Great advances have been 
made in immunology despite this lack of chemical knowledge; for these 
advances we are indebted to experimental biolog}^, through which we 
have learned the results of many effects without a knowledge of their 
nature or the intimate processes concerned. 

Natural Immunity. — Xatural immunity is an inherited character 
possessed in common by all individuals of a given species. It is in- 
herent to a greater or less extent in all members of that species. It 
may be present at birth or develop in later years. There are very many 
examples of natural immunity. Thus, most of the communicable in- 
fections of man are peculiar to man; that is, the lower animals have a 
natural immunity to such diseases as measles, mumps, scarlet fever, 
typhoid fever, cholera, gonorrhea, syphilis, yellow fever, malaria, 
leprosy, and so on through a long repertoire.^ Even tuberculosis, which 
is the most common and widespread of infections, has its own particu- 
lar bacillus to which man is especially susceptible and to whicli the 
lower animals show a marked degree of natural immunity. On the 
other hand, man shows a high grade of natural immunity to a large 
number of infections to which the lower animals are subject, as rinder- 
pest, black leg (symptomatic anthrax), Texas fever, etc. 

The monopoly which man possesses of being susceptible to infec- 
tions which the lower animals successfully resist is not confined to the 
bacteria alone, but includes many protozoa and higher animal parasites. 
Thus, the hookworm of man is different from the hookworm of the 
horse, the dog, the seal. Each host has its own species of hookworm 
which, though closely allied, are not interchangeable. That is, the 
horse has a natural immunity to the hookworm that is parasitic for 
man, and vice versa. 

There is a group of infections, including the pyogenic cocci, an- 
thrax, tetanus, malignant edema, glanders, actinomycosis, rabies, plague, 

^ It is true that some of these infections may be conveyed to monkeys or 
other animals by artificially introducing large amounts of the virus, but these 
animals do not contract these diseases naturally and therefore show a high degree 
of natural immunity. 


foot-and-mouth disease, malta fever, tuberculosis, milk sickness, infec- 
tions with the paratyphoid bacillus, ringworm, and many higher forms 
of animal parasites, which are common to many species in widely dif- 
ferent genera. 

There are certain remarkable facts connected with natural immu- 
nity. For example, white mice are susceptible to infections with the 
jmeumococcus, whereas the field mouse poss^esses a high degree of natu- 
ral resistance. When we consider how slight must be the differences 
in tlie structure, the function, the chemistry, and tlie metabolism in 
the white mouse when compared with its gray cousin, we begin to ap- 
preciate the subtle differences and perhaps complex factors upon which 
immunity depends. If we could find out, for example, why the goat is 
resistant to tuberculosis while domestic cattle are particularly suscep- 
tible, we would have the foundation for a specific preventive and cure 
for that disease. 

Practically all the individuals of a certain species have about an 
equal susceptibility or an equal immunity to a given infection. These 
factors are more constant than commonly supposed. Laboratory ani- 
mals react with certainty and with striking uniformity to an infection 
of known virulence, provided the virus is brought into association with 
certain tissues. Thus, strikingly uniform results are obtained from a 
given culture of plague introduced subcutaneously into the guinea pig, 
or of tuberculosis into the peritoneal cavity of the monkey, or of strep- 
tococci into the circulation of the rabbit, or of rabies under the dura 
of the dog, or of anthrax into the mouse. ]\Ian is no exception 
to this general statement, as far as may be judged from the data 
at hand. Practically all persons are alike susce])tible to smallpox, 
yellow fever, tetanus, and many other infections. In epidemics some 
individuals escape. In other epidemics the disease varies greatly 
in severity. These apparent exceptions may not be due so much to 
varying degrees of immunity, but rather to variations in the dose and 
virulence of the virus, the channel of infection, symbiosis, and other 

In some cases the immunity is so weak that the balance between 
health and disease is quite unstable. This appears to be tlie case with 
tuberculosis in man. We possess sufficient natural immunity to tuber- 
culosis successfully to resist small amounts of infection, but this re- 
sistance may readily be broken down by any influences which undermine 
our general vitality. 

Natural immunity may be broken down by various means that 
weaken the animal, such as fasting, the production of an experimental 
diabetes with phloridzin, fatigue, excessive cooling of the body, as the 
clipping of the hair of thick-furred animals, etc. Thus, chickens are 
ordinarily naturally immune to anthrax, but may be infected if their 


feet are kept in cold water. White rats are resistant to anthrax, but 
become susceptible if the hair is clipped. 

Acquired Immunity. — B}- acquired immunity is meant a specific re- 
sistance to an infection that is not naturally inherent in all the in- 
dividuals of a species, but, as the term indicates, the immunity is ac- 
quired during the lifetime of the individual. Immunity may be ac- 
quired either through some "natural" event, such as an attack of a dis- 
ease, or may be "artificially" induced by the introduction of some 
substance, such as a serum, toxine, vaccine, or a virus. 

Acquired immunity may be either active or passive. Active immu- 
nity is induced by an attack of a disease or by the introduction of a 
virus or suitable toxin into the system. Immunity thus acquired is 
active in the sense that it depends upon an aggressive stimulation of 
the protecting mechanism as a result of a series of reactions within the 
body. Passive immunitv, or transferred immunity, is an antitoxic im- 
munity. It is passive for the reason that the antibodies (antitoxin) 
are introduced into' the body, which, therefore, takes no part in their 
formation. The injection of diphtheria toxine into the horse causes an 
active immunity in that animal; the injection of some of the antitoxin 
contained in the horse's serum into a child causes a passive immunity in 
the child. Both are acquired because horse and man have no inherent 
or natural immunity to diphtheria. The protection against smallpox 
produced by vaccination is an example of active immunity; so also is 
the immunity produced by bacterial vaccines. 

Mixed Immunity. — Mixed immunity is a combination of the active 
and passive. This is used practically in plague prophylaxis and has 
been proposed for other infections. It consists in injecting a mixture 
of antitoxin serum and the appropriate bacterial virus. The advantage 
of this procedure consists in the fact that the active or antitoxin im- 
munity diminishes the severe reactions which sometimes follow the in- 
troduction of a bacterial virus. It also affords an immediate protection 
and thereby neutralizes the negative phase which is supposed to follow 
an active immunization. 

How Immunity May be Acquired.— Immunity may be acquired by: 

(a) An attack of a disease. 

(b) By the introduction of a virus. 

(c) By the introduction of a vaccine. 

(d) By the introduction of a chemical product (toxine). 

(a) An Attack of the Disease. — Certain diseases, whether acquired 
naturally or induced artificially, leave an immunity which varies greatly 
in degree and duration. The following diseases leave a definite immu- 
nity of high, though variable, grade: smallpox, yellow fever, measles, 
whooping-cough, scarlet fever, cerebrospinal meningitis, infantile paraly- 


sis, typhoid fever, typhus fever, chickenpox, mumps. Second attacks 
of smallpox, measles, typhoid fever, and other infections in this list 
are not uncommon, showing that the immunity is rarely if ever ab- 

Some diseases, such as pneumonia, erysipelas, and malaria, seem to 
predispose to subsequent attacks, that is, diminish resistance. Even in 
this class of infections there must be a certain amoimt of immunity, 
however short, else the patient would not recover. 

The practice of intentionally inoculating smallpox was the first ex- 
ample in preventive medicine in which use was made of the fact that 
one attack of a disease confers immunity to a subsequent attack of the 
same disease. The present-day vaccination of cowpox (a modified small- 
pox) may be considered as belonging to this category. The principle 
is used to a much greater extent in veterinary practice either by using 
a small amount of the infection or by introducing it in an unusual 
way or by inoculating the animals at a time when they are found to be 
least susceptible. In this way a benign form of the disease is produced 
which protects against the severe and fatal forms. These methods are 
used in Texas fever, rinderpest, pleuropneumonia, anthrax, etc. 

(b) By the Introduction of a Virus Into the System. — A distinc- 
tion is made between a virus and a vaccine. If the material used con- 
tains the living active principle it should be called a virus. If the 
virus is dead it should be called a vaccine.^ 

The highest and most lasting degrees of immunity may be produced 
by the introduction of the living active principle into the system, thus 
imitating nature. The virus may be diminished in virulence as in an- 
thrax, vaccinia, or rabies. A high grade of immunity to plague and 
cholera may be induced in man by the injection of living cultures. In 
the case of plague the cultures must be greatly diminished in virulence. 
In the case of cholera virulent strains nuiy be used, as this disease is 
neither a bacteremia nor septicemia, and there is very much less danger 
in introducing the cholera vibrios into the subcutaneous tissue than 
in taking them by the mouth. This principle of introducing the virus 
into a resistant tissue can be taken advantage of in various infections, 
provided the virulence of the disease depends largely upon the channel 
of infection. The virulence of the virus may also be diminished by 
certain definite processes, such as growing the culture at an unusually 
high temperature, as in the case of anthrax ; or by prolonged artificial 
cultivation, as in the classic instance of chicken cholera ; or by drying, 
as in rabies; or by passage through animals, as in smallpox (cowpox) ; 
or by growing on unfavorable media ; by the use of very small amounts 
of the virus, as in tuberculosis and many other infections; or by the 

^Vaccine (vacca, a cow) is not a good term, but is now too deeply rooted to 


use of closely related strains, such as the human tubercle bacillus for 
bovine immunization. Repeated injections of a virus induce a very high 
and more lasting immunity than single inoculations. 

(c) By the Introduction of a Bacterial Vaccine. — The immunity 
produced by the introduction of a vaccine into the body corresponds 
precisely to the immunity acquired by the introduction of a virus, the 
only difference being that the living virus produces a more lasting and 
higher degree of protection than that produced by the dead vaccine. 
The advantages of using a vaccine instead of a virus are obvious. 

Dead bacteria, when injected into the tissues, usually produce a local 
reaction at the site of inoculation and also a general reaction. The 
local reaction consists of swelling, pain, redness, and other indications 
of irritation and inflammation. The general reaction consists of fever, 
headache, pains in the muscles, especially in the back and legs, malaise, 
and sometimes nausea. The reactions usually come on within a few 
hours after the vaccine has been introduced and rarely last longer than 
24 to 48 hours. It is customary to give the vaccines in the evening, for 
then most of the symptoms have passed by the next morning. 

The vaccine is usually prepared from a fresh twenty-four-hour growth 
of a pure culture of the microorganism upon the surface of agar. In 
this way secondary metabolic products in the medium are avoided by 
simply removing the surface growth. When liquid cultures are used 
the foreign substances contained in the medium complicate the reactions. 
The cultures r,re usually killed by exposure to heat at from 53° to 60° C. 
for one hour. High heat, while certain to kill the virus, is undesirable, 
for the reason that it coagulates the albuminous substances in the germ 
cell and otherwise alters the chemical structure of the microorganism. 
The closer the vaccine approaches the virus the better the results, so 
far as immunity is concerned. Therefore, many investigators prefer to 
kill the poisons with carbolic acid, chloroform, or some other suitable 

The injections are always given subcutaneously. Usually three or 
four injections are given at intervals of about five to ten days. Several 
injections produce an immunity of much higher grade and longer dura- 
tion. In most instances the acquired immunity lasts from two to five 
years, and may be renewed. 

Preventive inoculations with bacterial vaccines are now much prac- 
ticed in the case of typhoid fever, plague, and cholera, and are destined 
to be extended to other infections. The dose and details have been 
discussed under each disease. 

A negative phase is said to follow the introduction of a vaccine or a 
virus; that is, a diminished resistance appears to be produced before the 
curve rises. The negative phase varies in degree, depending upon the 
amount and virulence of the vaccine and the power of the body to react. 


It varies in time from a few hours to several days. The negative phase 
is an assumption based upon a primary diminution in the amount of 
specific opsonins in the blood, but it is doubtful whether the opsonic 
index is a true index of the presence or absence of immunity, wliich is 
dependent upon other factors. From a practical standpoint, the negative 
phase can, as a rule, be disregarded ; that is, bacterial vaccines are not 
contraindicated during the period of incubation. 

Specificity.' — Most of the reactions in immunology are specific — 
not absolutely so, but relatively; that is, antibodies, such as agglutinins, 
lysms, precipitins, or opsonins, usually act upon the corresponding an- 
tigen with much greater vigor than upon any other. An immunity to 
one disease, no matter how produced, whether natural or acquired, af- 
fords no protection against other diseases. There is, however, no abso- 
lute specificity, just as there is no absolute immunity. 

Certain microorganisms and their toxic products show a remarkable 
predilection for certain cells or tissues. In this sense a microparasite 
or a toxin may be as specific in its action as a qualitative chemical re- 
action. Thus, there is a specific relation between tetanus toxin and 
nervous matter, while the poison has little or no affinity for other tis- 
sues. The poison of infantile paralysis picks out certain cells in the 
central nervous system upon which it acts specifically. Also in rabies 
the brunt of the lesions fall upon the cells of the central nervous sys- 
tem. The toxic products of the BacUJus hotidismus is also a specific 
nerve poison, and at least one of the poisons in diphtheria toxine (toxone) 
acts specifically upon the nerves. The toxic substances may also reacf 
upon less important or indifferent tissues, but such action is often 
masked. The specific action of toxins explains in part the local immu- 
nity enjoyed by some tissues and further explains why certain viruses 
are comparatively harmless when introduced into the body through 
unaccustomed channels. We have already seen an example of this in 
a case of cholera when introduced into the subcutaneous tissue. In 
this case the subcutaneous tissue is resistant to the invasion of the 
cholera vibrio, and these microorganisms cannot find their way to the 
intestinal tract. The case of smallpox is instructive, for this is an in- 
fection for which the epithelial structures have a specific susceptibility. 
It is practically impossible to infect a susceptible animal with cowpox 
when the virus is introduced subcutaneously or directly into the cir- 
culation. The same is probably true of smallpox. When smallpox 
virus is introduced by inoculation upon the skin the disease is much 
milder than when the virus is introduced by way of the respiratory 
tract. Evidently the skin offers greater resistance to the smallpox 
virus than is offered by the mucous membranes. On the other hand, 
foot-and-mouth disease cannot be given to man or the cow when rubbed 
upon the skin, although these animals are very susceptible when this 


virus is introduced into the general circulation or rubbed upon the mu- 
cous membrane of the mouth. Every worker in a bacteriological labora- 
tory is familiar -with the difference in susceptibility of different tis- 
sues and knows the imporiance in experimental work of bringing the 
virus in association with appropriate structures. 

Certain microorganisms, such as tuberculosis, pus cocci, the pneumo- 
coccus, etc., have the power of affecting almost every tissue and organ 
of the body. Xo part of the body is immune to the tubercle bacillus, 
but even in this infection some tissues are more susceptible than others. 
Thus, tuberculosis of the muscle is extremely rare ; the lungs and hnnph 
nodes are especially vulnerable. 

The stomach is comparatively rarely attacked by infective processes, 
although constantly exposed. The vaginal mucous membrane in the 
adult and the bladder are resistant to gonorrheal inflammations. There 
are many similar instances of specific immunity of tissues. 

The specific action of toxins gives us a ready reason why certain 
species of animals are immune to certain infections. In this case 
the immunity is not the result of any special or specific reaction, nor 
is it the result of any positive character possessed or acquired by the 
body, but is a negative trait entirely, due to the absence of specific 
chemical affinity between the cells and the toxin. The turtle is im- 
mune to tetanus because there is no combining affinity between the nerve 
cells of the turtle and tetanus toxin. The immunity, therefore, depends 
upon the absence of the appropriate cell receptors. Eats are highly 
immune to diphtheria toxin and hogs to snake venom. In these cases 
antitoxin cannot be demonstrated in the blood of the rat or the hog, 
and, so far as can be determined, when the toxin is injected into these 
animals it is not neutralized in the body. The simplest conception of 
the mechanism of immunity in these cases is to regard it as depending 
upon a negative factor resulting upon the absence of suitable receptors 
in the sense of Ehrlich's side-chain theory. 

Local and General Immunity. — Local and general immunity de- 
pends upon this variation in susceptibility of the different tissues to 
different infections. It is doubtful if there is a true general immu- 
nity in any case, for a general immunity is in almost all instances 
based upon a local resistance. Even antitoxic immunity in diphtheria, 
due to the antibodies in the general circulating blood, is the result 
of a localized neutralization in which many of the organs and tis- 
sues of the body take no part. There are many examples of local 
immunity. Trichina spiralis affects especially the muscles and never 
the bones. Diphtheria seldom extends down the esophagus. The most 
marked example, perhaps, is the almost perfect local immunity of the 
scalp to ringworm in adults, which contrasts so markedly with the ab- 
solute susceptibility of children, whereas the susceptibility of the skin 


of the body to the same parasite is, if anything, greater in adults than 
in children (Emery). 

Many remarkable instances of local immunity are shown by the tis- 
sues and must be familiar to all. Thus, erysipelas does not, as a rule, 
extend into the subcutaneous tissues, although the streptococcus may be 
there; rarely does it extend back into the area of the skin recently 

The immunity of a part is increased or diminished by the presence 
or absence of an adequate blood supply. As a rule, very vascular struc- 
tures enjoy a comparative immunity to infections which frequently 
attack other tissues relatively poor in blood supply. It may be stated 
as a general rule that the more copious the supply of healthy circulat- 
ing blood the greater the resistance to infection, and vice versa. This 
largely accounts for the local immunity enjoyed by the mucous mem- 
brane of the mouth and lips, which are constantly exposed to wound 
infections. Herein we also have an explanation of the utility of fo- 
mentations and other hot applications in the initial stages of an in- 
fective lesion. The same explanation is applied to Bier's method of 
passive congestion, in which an excess of blood (though partly stag- 
nant) is made to flush the tissues. The local immunity of the part 
may be diminished by a local anemia from any cause, by the presence 
of dead or injured tissue, by the action of irritants, trauma, etc. 

Metchnikoff has pointed out tliat in many infections general pro- 
tection is in inverse ratio to the local reaction at the site of introduc- 
tion of the virus. A severe and prompt local inflammatory reaction 
indicates an active power of protection. The increased volume of blood, 
the cells, the fluids of the blood and tissues are concentrated about the 
invading bacteria to wall them off and destroy them, that is the im- 
munity of the body against a general infection frequently depends upon 
the promptness and the activity of the local power of reaction. 

Some infections, notably streptococci, plague, or organisms belong- 
ing to the hemorrhagic-septicemic group, may invade the body with 
little or no local inflammatory reaction; that is, little or no barrier is 
set up against these microorganisms, they invade the blood and tissues 
without resistance and thus cause fatal septicemias. 

Bacillus Carriers or Immunitas Non Sterilans.— Upon recovery from 
an infective process the body usually rids itself completely of 
the infecting agent. In other words, the immunity which follows an 
attack of an infectious disease is usually associated with a power the 
body has of disinfecting itself. In most cases the patient is convales- 
cent or completely restored to health before the cause of the disease 
has disappeared from the tissues. This bespeaks a .vigorous protecting 
mechanism, but when this resistance is lowered for any reason a relapse 
may ensue. 


In many instances recovery takes place, but tlie living virulent 
microorganisms continue to live in the body. This constitutes immu- 
nity without sterilization, a term introduced by Ehrlich, though a 
more precise expression would be "immunity without disinfection." 
Such persons are now known as 'Tjacillus carriers." The immunity 
protects the carrier but endangers his fellownien. Bacillus carrying 
is common in diphtheria, typhoid fever, cholera, pneumonia, epidemic 
cerebrospinal meningitis, influenza, and many other bacterial infec- 
tions. Protozoon carriers are also a common phenomenon. The best 
examples are found in malaria, trypanosomiasis, Texas fever in cattle, 
etc. Analogous instances are also found in the higher parasitic worms 
in which the individual who carries the parasite is not affected. Thus, 
the negro and the Filipino show a relatively high degree of immunity 
to the hookworm and thus endanger their more susceptible white com- 

An acute bacillus carrier is one who sheds the specific agent of the 
disease for a few weeks — four to six following convalescence. A chronic 
bacillus carrier is one who harbors and discharges the specific agent a 
longer period than six weeks. A temporarij carrier is one who harbors 
the specific infective agent, although he himself has never had symp- 
toms of the disease. Temporary carriers may be acute or chronic, de- 
pending upon the length of time they harbor the particular parasite. 

Bacillus carriers play an important role in spreading infections. 
They explain many mysterious facts in the epidemiology of diphtheria, 
typhoid fever, cholera, cerebrospinal meningitis, malaria, etc. The 
bacillus carrier is sometimes a danger to himself. This is seen in diph- 
theria, pneumonia, influenza, and sometimes in typhoid and cholera. 
Thus, a person may carry the pneumococcus in his throat for years 
awaiting certain favorable conditions for infection before he contracts 
the disease. The same is more or less true of other carriers. 

While it is undoubtedly true that bacillus carriers play a very im- 
portant role in spreading infection from man to man, the relative im- 
portance compared with, other modes of transmission cannot be stated 
in percentage. The subject is still too young for definite quantitative 
figures. There is no doubt that bacillus carriers are more important 
in some diseases than others and play a variable role under different 
circumstances in the same disease. In our studies of typhoid fever 
in Washington one carrier was discovered in the examination of 986 
healthy individuals. This would mean approximately 300 typhoid 
bacillus carriers in the District of Columbia. If this proportion is cor- 
rect, it would account for the endemicity of typhoid fever in Washing- 
ton. Perhaps the residual typhoid fever in many places is largely kept 
alive through bacillus carrying, and there is little doubt that the grad- 
ual decline of typhoid fever after great sanitary reforms, such as the 


change from polluted to pure water, is due to the decrease in the number 
of carriers. It now seems evident that polluted water and infected milk 
will not always cause the disease directly in the persons drinking these 
fluids, but may produce numerous carriers who either contract the disease 
themselves subsequently or give it to others by passing the virus on in a 
more concentrated and virulent form, or to more susceptible individuals. 

It is evident from the nature of the case that the cure and control 
of bacillus carriers is one of the vital problems in preventive medicine. 
It is not only largely through them that infection is spread, but the 
infections themselves are kept alive in these carriers, who bridge over 
the interval between outbreaks. It is quite conceivable that with our 
modern methods of isolation and disinfection certain diseases would 
soon cease to exist were it not for immunitas non stenlans. 

Immunity is, therefore, a double-edged sword, in that it protects the 
carrier but endangers his neighbor. The control of bacillus carriers is 
a difficult problem. Such unfortunate persons cannot always be im- 
prisoned, nor is strict isolation always necessary. It is sufficient in the 
case of t}'phoid fever to restrict the activity of the carrier. Thus, a 
typhoid carrier should not cook, prepare, or handle food, or have any- 
thing to do with the production or distribution of milk. We have no 
satisfactory cure for carriers; this is a problem for the future; but 
their number may be lessened — this is a problem for the present. 

It should always be remembered that the number of carriers will 
diminish proportionately with the number of cases of any infection, 
and that every improvement in the water supply, the milk supply, the 
food supply, and our sanitary conditions generally will have a tendency 
to sharply diminish the number of carriers in any given infection. 
Therefore, while isolation, disinfection, and other methods used to 
control the spread of infection will never be completely successful as 
long as the carrier is omitted, nevertheless, these methods are entirely 
justified even though only partially useful. It is the duty of public 
health officers to check the spread of infection wherever it may be 
found. In time ready methods of recognizing bacillus carriers and 
means of neutralizing their potential danger will be more effective 
than is now possible. 

Latency is closely allied to bacillus carrying. The malarial para- 
site may remain latent in the spleen and other internal organs for 
years, during which time the person remains in good health. But 
when the resistance is reduced by exposure, fatigue, starvation, or other 
depressing influences the disease again breaks out. The gonococcus 
may also remain latent for years. I am familiar with one instance in 
which the tubercle bacillus remained latent in the axillary glands for 
10 years and then became active owing to a condition of depressed 
vitality. Typhoid ostitis may develop years after an attack of typhoid 


fever, and we can only assume that the bacilli have remained latent 
in the tissues all that time. The phenomenon of latency also occurs 
in rabies, tetanus, and other infections. 

Lowered Resistance. — The factors which lower our general resist- 
ance to disease are many and varied. The condition known as depressed 
vitality, lowered tone, general debility, weakened constitution, and 
terms of similar import imply a condition in which immunity is low- 
ered in a general and not in a specific sense. The principal causes 
which diminish resistance to infection are: wet and cold, fatigue, in- 
sufficient or unsuitable food, vitiated atmosphere, insufficient sleep and 
rest, worry, and excesses of all kinds. The mechanism by which these 
varying conditions lower our immunity must receive our attention, for 
they are of the greatest importance in preventive medicine. It is a 
matter of common observation that exposure to wet and cold or sudden 
changes of temperature, overwork, worry, stale air, poor food, etc., make 
us more liable to contract certain diseases. The tuberculosis propa- 
ganda that has been spread broadcast with such energy and good effect 
has taught the value of fresh air and sunshine, good food, and rest in 
increasing our resistance to this infection. 

There is, however, a wrong impression abroad that, because a low- 
ering of the general vitality favors certain diseases, such as tuber- 
culosis, common colds, pneumonia, septic and other infections, it 
plays a similar role in all the communicable diseases. Many infections, 
such as smallpox, measles, yellow fever, tetanus, whooping-cough, ty- 
phoid fever, cholera, plague, scarlet fever, and other diseases, have no 
particular relation whatever to bodily vigor. These diseases often strike 
down the young and vigorous in the prime of life. The most robust 
will succumb quickly to tuberculosis if he receives a sufficient dose of 
the virulent microorganisms. A good physical condition does not al- 
ways temper the virulence of the disease; on the contrary, many in- 
fections run a particularly severe course in strong and healthy subjects, 
and, contrariwise, may be mild and benign in the feeble. Physical 
weakness, therefore, is not necessarily synonymous with increased sus- 
ceptibility to all infections, although true for some of them. In other 
words, "general debility" lowers resistance in a specific, rather than in 
a general, sense. 

The mechanism by which the various causes that lower vitality and 
increase susceptibility act is in most cases quite obscure. Here is a field 
for laboratory research in immunology that offers rich reward of im- 
measurable practical good. Some of the factors concerned will be 
briefly discussed. 

Exposure to wet and cold, especially in combination, is a frequent 
source of lowered resistance. The exact way in which such exposure 
acts is not definitely known^ but laboratory researches offer material 


for a number of suggestions. Emery ^ sums up our knowledge upon 
this subject as follows: 

"Immunity is to a very large extent a function of the leukocytes, 
which are specialized cells to which the defense of the body is entrusted. 
Now, the functions (movement and phagocytosis) which can be easily 
investigated are found to be do])endent in a very high degree on tem- 
perature, acting best at the temperature of the body, or sliglitly above; 
and it is highly probable that the more subtle functions of the leuko- 
cytes may be similarly depressed by a low temperature. The exposure 
of the skin to cold, especially if the animal heat be abstracted more 
quickly by evaporation of moisture on the surface, will lead to a cool- 
ing of the blood which circulates through it, and hence to a slight, 
though appreciable, cooling of the whole blood. This, it is true, is 
soon compensated for, and no great amount of cooling of the whole body 
occurs; Ijut, even so, it is quite possible that the periodical chilling of 
the leukocytes during their repeated passages through the cold skin 
may be sufficient to diminish greatly their functional activity, and to 
lower the resistance to a point at which infection may occur, and when 
once pathogenic bacteria have gained a foothold the resistance will for 
a time tend to decrease. There is also some evidence going to show 
that exposure to cold may lessen the production of the defensive sub- 
stances which occur in the blood (alexin, antibodies, etc.), though this 
is not fully proved. It is worthy of note that the loss of immunity due 
to the action of cold and wet on one part of the body (such as the 
feet) is a general one, and may result in a nasal catarrh, an attack of 
pneumonia, acute rheumatism, etc., according to the nature of the in- 
fection at hand. It is not necessarily a local infection of the chilled 
region. This is very well shown experimentally. Fowls are immune 
to anthrax, but are rendered susceptible if they are kept for some time 
standing in cold water; and this acquired susceptibility is then a gen- 
eral one, and not merely of thp feet. 

"Cold and wet, as is well known, have less action when accompanied 
by energetic muscular exercise, so long as this does not reach the ex- 
tent of undue fatigue. This is not because less heat is lost during 
exercise. The reverse is the case. The suggested explanation is that 
the muscular metabolism leads to an increased production of heat, and 
at the same time the cutaneous capillaries are dilated and the heart 
accelerated, or that the circulation of blood through the skin occurs 
quickly; further, the internal temperature of the body may actually be 
raised several degrees. The result is tliat the temperature of any given 
leukocyte never falls much below normal, if at all, since it comes from 
the internal regions where the temperature is raised, passes rapidly 
through the skin, and returns again to the interior of the body, 

^"Immunity and Specific Therapy," 1909, p. 9. 


"The effect of fatigue, either alone or in conjunction with cold and 
wet, is also well known, and is one reason for the excessive mortality 
from disease of armies in the field. It is less explicable, but may prob- 
ably be connected in some way with the presence in the blood of kata- 
bolic products of muscular activity, which have an injurious action on 
the cells of the tissues in general and on the leukocytes in particular. 
Further, the metabolic products formed during the action of the muscles 
are acid in reaction, and it is found that some at least of the protective 
substances which occur in the blood (alexins and opsonins) act best 
in alkaline medium. This diminution of immunity after muscular 
fatigue is manifested in animals as well as in man. White rats which 
have been made to work in a revolving cage are more susceptible to 
anthrax than normal white rats, the preexisting immunit}^ being broken 

De Sandro ^ "injected dogs, rabbits, guinea pigs with typhoid toxins 
after severe muscular strain. Under the influence of the chemical 
changes induced by the physical strain, the nervous exhaustion, fatigue 
of the heart, and disturbances in the blood production, the defensive 
powers were evidently much weakened; phagocytosis was reduced and 
also the chemotactic power of the cells, the bacteriolysins, antitoxins, 
agglutinins, and opsonins showed a marked falling off." 

Insufficient and unsuitable food is a prime factor in undermining 
vitality and lowering resistance. Tlie influence upon health of food 
poor in quality or lacking in quantity is a matter of common experi- 
ence, but the scientific explanation of the way in which this result is 
brought about is not at all clear. First of all, it must be remembered 
that starvation or improper food does not' depress immunity to all 
infections, but lowers resistance only to certain infections. It was for- 
merly supposed that famine was the direct cause of pestilence. In 
fact, in India it has commonly been stated that "plague follows famine 
with some regularity," but we know now that plague in man is second- 
ary to the disease in rats and is transmitted through the flea. Ee- 
lapsing fever was formerly called famine fever, and outbreaks of ty- 
phus fever were frequently connected with famine, but we know now 
that the former is transmitted by the tick and the latter by the louse. 
It is evident that famine may be indirectly a cause of epidemic out- 
bursts without necessarily depressing immunity. Famine is usually 
accompanied by misery and squalor and an increase of vermin and other 
factors that favor the transmission of disease. 

Tuberculosis, of all diseases, is favored by insufficient and unsuit- 
able food. This is an infection in which poor nourishment lowers, 
and good nourishment raises, our immunity. Poor and insufficient food, 
however, is usually associated with poverty, insufficient clothing, un- 

"■Eiforma Medica, Naples, Aug. 1 & 8, Nos. 31 & 32. 


cleanly habits, vitiated atmosj)here. overwork, insufficient rest, and 
other depressing influences, so that it is difficult to assign relative im- 
portance to any one of these factors. For this reason we may perhaps 
be led to exaggerate its importance; and, wliile it is, of course, true 
that semistarvation, in common with other weakening influences, does 
pave the way for infective processes, we do not find that a supply of 
food restricted enough to cause a marked reduction of the bodily strength 
and some degree of anemia is necessarily associated with any infective 
disease, though the patient may live under conditions in which infec- 
tive material is present in abundance. This is well seen in fasting 
men, in hysterical anorexia, and in patients with impermeable esopha- 
geal strictures. The blood, it may be pointed out, is not one of the 
tissues that suffers first in starvation, and its importance to the body 
in many ways is so great that it is kept in good functional activity 
while other tissues waste quickly. 

There is a general belief that exposure to infection is less dangerous 
after a meal than upon an empty stomach. There is little ground for 
this belief, unless we take into consideration the notable increase in the 
number of leukocytes in the peripheral blood during active digestion. 
It was recognized long ago that wounds inflicted during autopsies are 
much more dangerous when received while fasting than during the 
process of digestion, and it is possible that this may be due to some 
extent to the increased number of leukocytes which occur in the blood 
during the process. Further, infection reaching an empty stonuich has 
greater chances of passing into the small intestines than if it reaches the 
stomach after a full meal when acidity, time, and the digestive enzymes 
have a chance to destroy the microorganisms. This may be of impor- 
tance in cholera, typhoid, dysentery, and other intestinal infections. 

Exposure to a vitiated atmosphere, if of long duration, is one of 
the potent causes of breaking down resistance. Here again, however, 
immunity is lowered in a specific and not in a general sense. Thus, 
vitiated air renders the individual more susceptible to tuberculosis, 
pneumonia, common colds, and other acute respiratory affections. On 
the other hand, it can have little influence in determining the infec- 
tion of most of the communicable diseases, although the lowered tone 
of the body caused by vitiated air may influence the severity of the 
attack. The mechanism by which vitiated air increases susceptibility 
is not understood at all. The subject is discussed in the chapter upon 

Excesses of all kinds, symbolized by Bacchus, Venus,* and Vulcan, 
are mighty factors in lowering vitality and in increasing susceptibility 
to certain diseases. In this category are also found worry, overwork, 
loss of sleep, and fatigue. 

Certain drugs, of which the most important is alcohol, have an im- 


portant action in lowering resistance. Emery states that: "The liabil- 
ity of alcoholic subjects to pneumonia and some other infective dis- 
eases is well known, and in them the prognosis is more than usually 
unfavorable. We have but little knowledge of the action of alcohol in 
this respect. It may be that it acts as a direct inhibitant of the ac- 
tivity of the leukocytes, and it is known to destroy certain delicate de- 
fensive substances (alexins and opsonins) which play some part in the 
defense of the body against microbic invasion, but it is not known 
-whether these effects are actually manifested in the circulating blood. 
It is also possible that alcohol tends to inhibit the formation of these 
defensive substances. 

"Alcohol tends to lower the temperature of the body by increasing 
the amount of heat lost. It dilates the superficial vessels and accelerates 
the heart action in a way somewhat similar to muscular exercise, but 
does not, like it, raise the temperature of the interior of the body. 
Hence the effect of alcohol in conjunction with cold and wet is to in- 
crease their ill effects. More blood is forced through the chilled skin 
and more heat is lost. The injurious effect of alcohol during exposure 
to cold is well known. The results, however, are different when al- 
cohol is taken after exposure, and when the sufferer has reached warmth 
and shelter. There the increased flow in the cutaneous capillaries leads 
to a warming of the skin and consequent cessation of the chi